SEC Form DEF 14A filed by S&T Bancorp Inc.

To my fellow shareholders:   S&T Bank was founded in 1902 on a simple but enduring belief: banking should begin and end with people. As we embark on 125 years, that principle continues to shape how we serve our customers, invest in our communities and create long-term value for our shareholders through our people-forward approach to banking.   Our strategic framework, Our Shared Future, remains the foundation for disciplined execution and sustainable performance. It clarifies our purpose, sharpens our priorities and aligns our teams around profitable growth, prudent risk management and operational excellence. In 2025, we continued to turn strategy into measurable progress, strengthening our organization while positioning the Bank for sustained success in the years ahead.

2025 Performance and Strategic Progress

Throughout 2025, we advanced our key business drivers with focus and consistency. We delivered solid return metrics with return on tangible equity (non-GAAP) of 12.62% and return on assets of 1.38%. These returns were supported by total loan growth of $329 million and $220.5 million of customer deposit growth (total deposit growth of $175.7 million). S&T serves 132,000 households in Pennsylvania and Ohio with over 1,200 team members at more than 70 locations, reflecting intentional growth and expansion since our founding in Indiana, Pennsylvania. Importantly, our progress continues to be relationship-driven and supported by ongoing improvement in asset quality, strong capital levels and consistent growth in our customer deposit franchise.

A Culture That Delivers Results

At S&T, our culture is not just aspirational language; it is a true competitive advantage and woven into the fabric of who we are. Our team members bring our people-forward purpose to life by building trust, strengthening relationships and delivering thoughtful financial solutions. We are guided by our values, which define how we operate every day and turn purpose into action and strategy into meaningful results:

Our investment in our people is a strategic driver of our long-term success and enables our employees to deliver meaningful results for our customers, shareholders and communities. The external recognition we received in 2025 reflects the strength of that culture and underscores its impact across our organization.

The Bank has earned the following recognitions, to name a few:

These awards affirm that when we invest in our people, performance follows.

Community Impact

We believe financial performance and community impact are mutually reinforcing. In 2025, our employees once again demonstrated extraordinary commitment to the communities we serve.

Through employee giving campaigns and corporate philanthropy, S&T contributed:

Additionally, we provided $26.6 million in community development loans to support affordable housing initiatives, small business growth and revitalization efforts across our footprint.

These investments reflect our belief that strong communities create stronger economies and a stronger Bank.

Financial Highlights

The strength of our culture, combined with disciplined execution, produced solid financial results in 2025.

Financial highlights for the year include**:

Our performance also earned notable external recognition in 2025. S&T was named as one of Forbes* America’s Best Banks in 2025 for the third consecutive year, ranking 36 on the list and the highest-ranked bank headquartered in Pennsylvania. This is reflective of the strength of our profitability, capital, asset quality and shareholder returns as well as a meaningful validation of the Bank’s consistency and discipline behind its strategy and the collective drive and shared sense of purpose of its employees.

Positioning for the Future

The financial services industry continues to evolve, shaped by technological advancement, shifting customer expectations and a dynamic economic environment. We are investing strategically in digital capabilities, technology, talent development and our security and risk infrastructure to ensure we remain competitive and responsive.

While markets change, our foundation and people-forward banking purpose does not. We remain committed to disciplined growth, strong credit quality, capital strength and prudent expense management. Most importantly, we remain committed to earning the trust placed in us and building on Our Shared Future.

Christopher McComish

Chair and CEO

Lead Independent Director Letter to Shareholders   Dear Shareholders,   It is a privilege to write to you for the first time in my role as Lead Independent Director of S&T Bancorp, Inc. I am grateful for the confidence my fellow directors have placed in me and honored to serve our shareholders in this capacity.   In late 2025, following the resignation of long-serving Chair Christine J. Toretti, who became an Ambassador to Sweden, the board appointed our Chief Executive Officer, Christopher J. McComish, to also serve as chair and established the role of lead independent director to strengthen independent oversight and effective governance.   Maintaining a balanced and engaged board remains a priority. Our independent directors represent a broad range of professional backgrounds and experiences. Together, these perspectives enhance the board’s ability to engage constructively with management and provide thoughtful strategic guidance on behalf of our shareholders.

In October, we were pleased to welcome Stephanie N. Doliveira as a new independent director. Her experience at a large regional convenience retailer provides the board with deep expertise in culture and workforce strategy. In addition, her background in legal, regulatory and enterprise risk matters brings valuable perspective as the board continues to oversee the Bank’s strategy, risk framework and long-term planning.

S&T’s board structure provides unified leadership while maintaining a clear framework for strong independent oversight. As lead independent director, I work closely with the chair and my fellow independent directors to ensure the board maintains an independent perspective in its deliberations and effectively fulfills its oversight responsibilities.

The board recognizes that its role is distinct from that of senior management. While management leads the Bank’s day-to-day operations, the board provides strategic oversight and guidance by fostering open and constructive dialogue, challenging management when appropriate and helping position the Bank for long-term success. Our discussions regularly address financial performance, geopolitical developments, the evolving regulatory environment and emerging technologies such as artificial intelligence. Key matters, including liquidity, capital strength, cybersecurity, risk management and the broader economic landscape, are reviewed consistently across board and committee meetings.

As a board, our work is guided by the same people-forward purpose and values that define the Bank and shape how it serves customers, supports employees and strengthens the communities in which it operates.

The board also oversees the execution of the Bank’s strategic framework, Our Shared Future, which emphasizes deepening customer relationships, investing in people and capabilities, and pursuing disciplined, sustainable growth. Through ongoing engagement and the work of our board committees, we oversee the development and execution of the Bank’s strategy and help ensure management’s actions remain aligned with the Bank’s long-term objectives and the interests of our shareholders.

Our board remains committed to strong governance, active engagement and supporting the lasting success of the Bank. The Bank is well-positioned to advance its strategic priorities while delivering lasting value for all stakeholders.

On behalf of the entire board of directors, thank you for your continued support and confidence in S&T Bancorp, Inc. and S&T Bank. We appreciate your investment and remain focused on serving the best interests of our customers, colleagues, communities and shareholders.

Sincerely,

Jeffrey Grube

Lead Independent Director

Board of Directors

S&T Bancorp, Inc.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF

PROXY MATERIALS FOR THE 2026 ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD ON MAY 12, 2026: OUR PROXY STATEMENT, 2025 ANNUAL REPORT AND NOTICE OF

ANNUAL MEETING OF SHAREHOLDERS ARE AVAILABLE AT WWW.PROXYVOTE.COM

We are taking advantage of a rule of the Securities and Exchange Commission (the “SEC”) which allows companies to make proxy materials available on a public website rather than in paper form. This rule allows a company to send some or all of its shareholders a Notice of Internet Availability of Proxy Materials (“Notice”) in place of the complete proxy package. For our 2026 Annual Meeting, to save significant printing and mailing expenses, S&T mailed a Notice to certain shareholders who had not previously elected to receive their proxy materials through the mail on or about March 30, 2026, to inform them of the electronic availability of the proxy materials 40 days in advance of the Annual Meeting.

TABLE OF CONTENTS

S&T BANCORP, INC.

PROXY STATEMENT FOR

ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD MAY 12, 2026

INTRODUCTION

This proxy statement (“Proxy Statement”) is being furnished to shareholders of S&T Bancorp, Inc. in connection with the solicitation of proxies by the Board of Directors of S&T (the “S&T Board” or “Board”) for use at the Annual Meeting, and any adjournments thereof, to be held at the time and place set forth in the accompanying notice. We are first sending the Notice of Internet Availability of Proxy Materials (“Notice”), or this Proxy Statement, S&T’s 2025 Annual Report and proxy card to shareholders on or about March 30, 2026.

At the Annual Meeting, shareholders of S&T will be asked to (i) elect 11 directors of S&T to serve a one-year term, (ii) approve the ratification of the selection of Ernst & Young LLP as S&T’s independent registered public accounting firm for the fiscal year 2026, and (iii) approve, on a non-binding advisory basis, the compensation of S&T’s named executive officers (“NEOs”).

MEETING INFORMATION

Date, Time and Place

The Annual Meeting will be held on May 12, 2026, at 10:00 a.m. Eastern Time solely online via the Internet by going to www.virtualshareholdermeeting.com/STBA2026. To participate in the Annual Meeting, you will need the 16-digit control number included on your Notice, on your proxy card or on the instructions that accompanied your proxy materials. See “Attending the Meeting; Virtual Meeting” below.

As permitted by S&T’s By-laws and applicable law, S&T will hold a virtual-only Annual Meeting. S&T will continue holding annual meetings in virtual-only format so long as shareholders are served well through this medium, which we believe enhances accessibility to our Annual Meeting for all of our shareholders.

Record Date, Voting Rights and Required Vote

The securities that can be voted at the Annual Meeting consist of shares of common stock of S&T, par value $2.50 per share (“Common Stock”), with each share entitling its owner to one vote on each matter to be voted on at the Annual Meeting. There are no cumulative voting rights with respect to the Common Stock. Only holders of the Common Stock at the close of business on February 27, 2026 (the “Record Date”) are entitled to notice of and to vote at the Annual Meeting. There were 36,645,012 shares of Common Stock outstanding as of the Record Date.

A quorum is required for the transaction of business at the Annual Meeting. A “quorum” is the presence at the meeting, virtually (i.e., online via www.virtualshareholdermeeting.com/STBA2026) or represented by proxy, of the holders of the majority of the outstanding shares of Common Stock entitled to vote at the meeting. Abstentions are counted for purposes of determining the presence or the absence of a quorum but are not considered a vote cast under Pennsylvania law. Under our governing documents and applicable state law, abstentions will not affect the outcome of a vote on a particular matter. Broker non-votes are counted to determine if a quorum is present but are not considered a vote cast under Pennsylvania law. Under our governing documents and applicable state law, broker non-votes will not affect the outcome of a vote on a particular matter. Generally, broker non-votes occur on a matter when a bank, broker or other nominee is not permitted to vote on that matter without instructions from the beneficial owner and such instructions are not

S&T Bancorp, Inc. | 2026 Proxy Statement | 1

Meeting Information

given. Banks, brokers and other nominees have discretionary authority to vote shares in the absence of instructions on matters considered “routine,” such as the ratification of the appointment of the independent registered public accounting firm. They do not have discretionary authority to vote shares in the absence of instructions on “non-routine” matters, such as the election of directors and the advisory vote on compensation of S&T’s NEOs.

The director nominees will be elected by a plurality of the votes cast at the Annual Meeting, which means that the 11 nominees receiving the most votes will be elected. A withheld vote on any nominee will not affect the voting results. Under S&T’s voting standard policy adopted by the S&T Board, which is included in S&T’s Corporate Governance Guidelines (“Guidelines”), if a director nominee in an uncontested election at the Annual Meeting receives a greater number of “withheld” votes from his or her election than votes “for” such election, such director must submit his or her resignation to the Board promptly following the certification of election results. The resignation will first be considered by the members of the Nominating and Corporate Governance Committee (the “Nominating Committee”) within 60 days following certification of the shareholder vote. The Nominating Committee will recommend to the S&T Board whether to accept or reject the resignation after considering all factors deemed relevant by the Nominating Committee. The S&T Board shall act on the Nominating Committee’s recommendation within 90 days following certification of the shareholder vote. If a director’s resignation is accepted by the Board, the Board either may fill the resulting vacancy or may decrease the size of the Board pursuant to S&T’s By-laws.

The ratification of the selection of Ernst & Young LLP as S&T’s independent registered public accounting firm for fiscal year 2026 and the approval, on a non-binding advisory basis, of the compensation of S&T’s NEOs require the affirmative vote of a majority of the votes cast at the Annual Meeting to be approved.

Voting and Revocation of Proxies

Shareholder of Record. If you are a shareholder of record and you received the Notice, you may vote before the Annual Meeting by accessing the secure Internet website registration page identified on the Notice and following the instructions. You may also vote electronically during the virtual Annual Meeting if you participate.

If you are a shareholder of record and you received a printed copy of the proxy materials, you may vote by proxy by telephone, using the Internet or by mailing your proxy card, as further described below. You may also vote electronically during the virtual Annual Meeting if you participate.

If you vote by proxy via telephone or the Internet, you do not need to mail your proxy card. The individuals named as proxies on your proxy card will vote your shares of Common Stock during the Annual Meeting as instructed by the latest dated proxy received from you, whether submitted via the Internet, telephone or mail. If you sign your proxy card but do not specify how you want your shares voted on any matter, you will be deemed to have directed the proxies to vote your shares as recommended by the S&T Board.

Beneficial Owners. If your shares of Common Stock are held in a stock brokerage account by a bank, broker or other nominee, you are considered the beneficial owner of shares held in street name and these proxy materials

2 | S&T Bancorp, Inc. | 2026 Proxy Statement

Meeting Information

are being forwarded to you by your bank, broker or other nominee that is considered the shareholder of record of those shares.

As the beneficial owner, you have the right to direct your bank, broker or other nominee on how to vote your shares of Common Stock via the Internet or by telephone, if the bank, broker or other nominee offers these options, or by completing, signing, dating and returning a voting instruction form. Your bank, broker, or other nominee will send you instructions on how to submit your voting instructions for your shares of Common Stock.

If you properly complete, sign, date and return the voting instruction form, your shares of Common Stock will be voted as you specify. If you are a beneficial owner and you do not provide voting instructions to your bank, broker or other nominee holding shares of Common Stock for you, your shares of Common Stock will not be voted with respect to any proposal for which the shareholder of record does not have discretionary authority to vote.

Except for procedural matters incident to the conduct of the Annual Meeting, S&T does not know of any matters other than those described in the Notice of Annual Meeting of Shareholders that are to come before the Annual Meeting. If any other matters are properly brought before the Annual Meeting, the persons named in the proxy will vote the shares represented by the proxies in their discretion on such matters as recommended by a majority of the S&T Board.

Revocation of Proxies. The presence of a shareholder at the virtual Annual Meeting will not automatically revoke such shareholder’s proxy. However, a shareholder may revoke a proxy at any time prior to its exercise by filing with the Secretary of S&T a written notice of revocation, by delivering to S&T a duly executed proxy bearing a later date or by voting electronically during the virtual Annual Meeting.

Attending the Meeting; Virtual Meeting

You may attend the webcast of the meeting via the Internet at www.virtualshareholdermeeting.com/STBA2026 when you enter the 16-digit control number included on your Notice, on your proxy card or on the instructions that accompanied your proxy materials. Instructions on how to attend and participate in the Annual Meeting via the webcast are posted at www.virtualshareholdermeeting.com/STBA2026. You will be able to vote your shares while attending the Annual Meeting by following the instructions on the website. Our management will address questions from shareholders who have submitted their questions electronically prior to and during the Annual Meeting. You may visit www.proxyvote.com at any time prior to the Annual Meeting to ask questions of our executive management that may be addressed in the Annual Meeting and access information about S&T. Even if you plan to participate in the Annual Meeting, we urge all shareholders to vote on the matters listed above and described in the Proxy Statement as soon as possible, so that your vote will be counted if you later decide not to participate in the Annual Meeting.

Solicitation of Proxies

The cost of soliciting proxies will be borne by S&T. S&T has engaged D.F. King & Co., Inc. to help solicit proxies for the Annual Meeting, and will pay D.F. King & Co., Inc. $10,500, plus its out-of-pocket expenses, for the solicitation of proxies. In addition to the solicitation of proxies by mail, S&T may also solicit proxies personally, by telephone or by electronic means, through its directors, officers and regular employees. None of these directors, officers or employees will receive any additional or special compensation for soliciting proxies. S&T also will request persons, firms and corporations holding shares of Common Stock in their names or in the name of their nominees, which are beneficially owned by others, to send proxy materials to and obtain proxies from the beneficial owners and will reimburse the holders for their reasonable expenses in so doing.

Internet Availability of Proxy Materials

S&T’s Proxy Statement for the Annual Meeting and S&T’s 2025 Annual Report are available at www.proxyvote.com. You will enter your 16-digit control number included on your Notice, on your proxy card or on the instructions that accompanied your proxy materials to access these materials.

S&T Bancorp, Inc. | 2026 Proxy Statement | 3

Meeting Information

Householding

The SEC has adopted rules that permit companies and intermediaries (e.g., brokers) to satisfy the delivery requirements for Notices or proxy statements and annual reports with respect to two or more shareholders sharing the same address by delivering a single Notice or proxy statement and annual report addressed to those shareholders. This process is commonly referred to as “householding.”

S&T has implemented “householding” to reduce the number of duplicate mailings to the same address. This process benefits both shareholders and S&T because it eliminates unnecessary mailings delivered to your home and helps to reduce S&T’s expenses. “Householding” is not being used, however, if S&T has received contrary instructions from one or more of the shareholders sharing an address. If your household has received only one Notice or one annual report and proxy statement, S&T will deliver promptly a separate copy of the Notice or annual report and proxy statement to any shareholder who contacts S&T by calling the toll-free number, 1-800-325-2265, or by mail to the attention of the Secretary of S&T at 800 Philadelphia Street, Indiana, Pennsylvania 15701. You can also notify S&T that you would like to receive separate copies of the Notice or S&T’s annual report and proxy statement in the future by calling or mailing S&T, as instructed above. If your household has received multiple copies of the Notice or S&T’s annual report and proxy statement, you can request the delivery of single copies in the future by calling or mailing S&T, as instructed above, or your broker, if you hold the shares in “street name”.

If you received more than one Notice or proxy card, it means that your shares are registered in more than one name (e.g., trust, custodial accounts, joint tenancy) or in multiple accounts. Please make sure that you vote all of your shares by following the directions on each Notice or on each proxy card that you received.

For our 2027 annual meeting, you can help us save significant printing and mailing expenses by consenting to access our proxy materials electronically via the Internet. If you hold your shares in your own name (instead of “street name” through a bank, broker or other nominee), you can choose this option by following the prompts for consenting to electronic access, if voting by telephone, or by following the instructions at the Internet voting website at www.proxyvote.com, which has been established for you to vote your shares for the 2026 Annual Meeting. If you choose to receive your proxy materials electronically, then prior to next year’s annual meeting, you will receive notification when the proxy materials are available for online review via the Internet, as well as the instructions for voting electronically via the Internet. Your choice for electronic distribution will remain in effect until you revoke it by sending a written request to S&T by mail to the attention of the Secretary of S&T at 800 Philadelphia Street, Indiana, Pennsylvania 15701. If you hold your shares in “street name” through a bank, broker or other nominee, you should follow the instructions provided by that entity if you wish to access our proxy materials electronically via the Internet.

4 | S&T Bancorp, Inc. | 2026 Proxy Statement

BENEFICIAL OWNERS OF S&T COMMON STOCK

Under Section 13(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), a beneficial owner of a security is any person who directly or indirectly has or shares voting power or investment power over such security. Such beneficial owner under this definition need not enjoy the economic benefit of such securities. The following are the only shareholders known to S&T to be deemed to be a beneficial owner of 5% or more of Common Stock as of February 27, 2026, when 36,645,012 shares of Common Stock were outstanding. S&T has relied solely on information provided in the public filings made by the holders below:

S&T Bancorp, Inc. | 2026 Proxy Statement | 5

BENEFICIAL OWNERSHIP OF S&T COMMON STOCK BY DIRECTORS AND OFFICERS

The following table sets forth, as of February 27, 2026, the amount and percentage of Common Stock beneficially owned by each director, each nominee for director and each of the “NEOs” (as defined below) of S&T, as well as the directors and executive officers of S&T as a group. Unless otherwise indicated, all persons listed below have sole voting and investment power over all shares of Common Stock. The business address of each of S&T’s directors and officers is 800 Philadelphia Street, Indiana, Pennsylvania 15701.

6 | S&T Bancorp, Inc. | 2026 Proxy Statement

Beneficial Ownership of S&T Common Stock by Directors and Officers

Delinquent Section 16(a) Reports

Section 16(a) of the Exchange Act requires S&T’s directors and executive officers, and beneficial owners of more than 10% of Common Stock to report to the SEC certain of their transactions with respect to S&T’s Common Stock. We assist our directors and officers by monitoring transactions and completing and filing these reports on their behalf.

To our knowledge, based solely on a review of the reports filed for fiscal year 2025 and written representations that no other reports were required, during the fiscal year ended December 31, 2025, all Section 16(a) filing requirements applicable to our executive officers, directors and greater than 10% beneficial owners were filed in a timely manner, except as follows: (a) due to an administrative issue involving a software program, filings on Form 4 for Mr. Antolik, Mr. Drahnak, Mr. Kochvar, Ms. Lazzari, and Ms. Yesho to report annual restricted stock unit awards were filed one day later than required on April 4, 2025, and (b) due to a delay in receiving an updated filing password from a company with which S&T shares form reporting requirements, a filing on Form 4 to report an exercise of the vesting of the award for Mr. Ramachandran was filed one day later than required on May 16, 2025. Additionally, in the course of its review, S&T identified that a 2022 tax withholding transaction on Form 4 was not previously filed for Mr. McComish due to an administrative oversight. Upon discovery of the error, a corrective filing on Form 4/A was promptly filed.

S&T Bancorp, Inc. | 2026 Proxy Statement | 7

PROPOSAL 1: ELECTION OF DIRECTORS

General

The S&T Board determines the number of directors to nominate for election. The By-laws of S&T provide that the number of directors constituting the Board will consist of not less than nine nor more than 17, with the exact number to be fixed and determined from time to time by resolution of a majority of the Board. For this Annual Meeting, the Board fixed the number of directors to be elected at 11.

There are currently 11 directors comprising the Board. The Board has nominated the 11 persons named below for election at the Annual Meeting, all of whom are incumbent directors standing for re-election. Proxies cannot be voted for a greater number of persons than the number of nominees named in this Proxy Statement.

The Nominating Committee recommended each of the nominees to the Board. Directors are elected annually, and each director nominee elected at the Annual Meeting will serve for a term expiring at the 2027 S&T annual meeting of shareholders, until his or her successor has been elected and qualified, or until his or her earlier death, resignation, removal or disqualification. All nominees have indicated their willingness to serve, if elected, but if any should be unable to serve or unwilling to serve for good cause, proxies may be voted for a substitute nominee designated by the Board. There are no family relationships between or among any of our directors, executive officers or persons nominated or chosen to become a director or executive officer. Unless otherwise instructed, the proxy holders will vote the proxies received by them for the nominees named below.

Set forth below is a brief description of the principal occupation and business experience of each of our nominees for director, as well as a summary of the qualifications of each nominee and continuing director to serve on the Board. The Board has had significant experience with each of the incumbent directors and has had the opportunity to assess the contributions that each director has made to the Board as well as each director’s industry knowledge, judgment and leadership capabilities. The Nominating Committee continually assesses the composition of the Board and seeks opportunities, within the constraint of the size of the Board, to include a mix of directors with Board experience and with fresh perspectives. The average tenure of the current Board is 8.5 years and S&T’s By-Laws and Guidelines include a mandatory director retirement age of 72. In 2025, the Nominating Committee had the opportunity to add one new director, Stephanie N. Doliveira, to the Board to further strengthen the Board’s knowledge, experience, judgment and leadership capabilities. The Board has two female directors, one African American director and one Asian director.

S&T seeks director candidates who will uphold the highest standards, are committed to S&T’s values, and who will be strong independent stewards of the long-term interests of shareholders. In selecting nominees, our Board looks for individuals with demonstrated experience and success in fields that are relevant to our business, strategy and operations, and who will contribute diverse viewpoints and perspectives.

In evaluating and selecting nominees to the Board, our Nominating Committee considers all factors and criteria it deems appropriate, including, but not limited to, the factors set forth in our Guidelines. See the section “Director Qualifications and Nominations” below for further information on our director selection process and criteria. In furtherance of the foregoing, the Board considers a wide range of attributes when selecting and recruiting candidates. All nominees possess integrity, judgment, strong work ethic, collaborative approach to engagement and oversight, inquisitive and objective perspective, and a willingness to challenge management

8 | S&T Bancorp, Inc. | 2026 Proxy Statement

Proposal 1: Election of Directors

appropriately. In addition, our nominees have executive experience and skills that are aligned with our business and strategy, including the following:

Director Nominees for Election at the 2026 Annual Meeting:

		Lewis W. Adkins, Jr., Age 62
		Director since 2019		Committees: • Compensation & Benefits • Credit Risk • Nominating & Corporate Governance

Biographical Information

Mr. Adkins is a Shareholder and Shareholder-in-Charge of Development & Practice Integration for Roetzel & Andress, LPA, a full-service law firm with offices located throughout Ohio, Florida and Chicago. Additionally, since May 2017, he has served as President of their wholly-owned consulting subsidiary, Roetzel Consulting Solutions, a bipartisan consulting company representing clients where the private and public sectors intersect. Mr. Adkins previously served as General Counsel to Summit County, Ohio. He is affiliated with numerous professional and charitable organizations including Board Chair and President for the University of Akron Board of Trustees, Ideastream Public Media Board of Trustees, the American Bar Association, the Greater Akron Chamber of Commerce, Alpha Phi Alpha Fraternity, Inc. and the Cleveland Metropolitan Bar Association.

Experience and Qualifications

Mr. Adkins also has acted as lead counsel for several multi-million-dollar development projects. His clients include public and private entities, as well as construction companies, engineering firms, financial institutions, diversified energy companies, governmental entities, housing authorities, urban school districts and nonprofit organizations. Prior to assuming his current leadership role, Mr. Adkins led for over a decade Roetzel & Andress, LPA’s Public Law and Finance team as Practice Group Manager. Additionally, he is currently General Counsel to Alpha Phi Alpha Homes, Inc. He also serves as lead counsel for a number of public and private entities including Ohio’s largest banking institution, a regional public hospital and two of Ohio’s largest school districts. Mr. Adkins’ expansive business and legal knowledge and his community leadership provide the S&T Board with public finance, business development, and strategic management experience which qualifies him to serve on the S&T Board.

S&T Bancorp, Inc. | 2026 Proxy Statement | 9

Proposal 1: Election of Directors

Biographical Information

Mr. Antolik has been President of S&T and S&T Bank since January 2019. He was Interim Chief Executive Officer and President from April 1, 2021 to August 23, 2021. Mr. Antolik was Chief Lending Officer of S&T and S&T Bank from 2008 to October 2020. He previously served as Senior Executive Vice President of S&T and S&T Bank from 2008 until January 2019. Mr. Antolik also serves as the chairman of the IUP Research Institute and is a member of the Indiana County Development Corporation Board.

Experience and Qualifications

With 37 years of banking experience, including 18 years of senior management experience at S&T, Mr. Antolik’s strong leadership capabilities and in-depth industry experience in commercial banking and implementing strategic initiatives provide the S&T Board with expertise that will contribute to the strategic growth of S&T. As our past Interim Chief Executive Officer and current President, Mr. Antolik provides unique insight to the S&T Board regarding our day-to-day operations, customer information, competitive intelligence, general trends in national and local banking and issues regarding our financial results.

Biographical Information

Mr. Barsz is a Certified Public Accountant and has been a Partner at Barsz Gowie Amon & Fultz, LLC, an accounting firm, since July 2017 when Steger Gowie & Company merged with Merves Amon & Barsz LLC where Mr. Barsz became a partner in 1990. Mr. Barsz previously served on the board of DNB, the holding company for DNB First, N.A., from January 2018 until it was acquired by S&T in November 2019. Mr. Barsz serves as the appointed Treasurer and has served as the Finance Director of several municipalities in Chester and Delaware counties and is currently serving as Chairman of the Pennsylvania State Tax Equalization Board, an independent agency of the Commonwealth tasked with obtaining information on real estate sales throughout the state.

Mr. Barsz also received an appointment by the Pennsylvania Legislature and is currently serving as a public member on the Legislative Audit Advisory Committee for the current and past three Legislative Sessions of the General Assembly. Mr. Barsz previously served as a director of two real estate holding companies located in Media, Pennsylvania as well as the Treasurer of the Foundation of the Delaware County Chamber of Commerce. Mr. Barsz was appointed by the Delaware County Court of Common Pleas to act as the Independent Trustee of a Family Trust. Mr. Barsz was also recently appointed to the board of the Drexel Neumann Academy, which is an independent parochial school educating children from Kindergarten to eighth grade, located in Chester, Pennsylvania.

Experience and Qualifications

Mr. Barsz’s extensive experience in accounting and providing management and financial consulting services to governmental and nonprofit entities, his deep community engagement, as well as his broad financial perspective qualify him to serve on the Audit Committee as an “audit committee financial expert” and on the S&T Board.

10 | S&T Bancorp, Inc. | 2026 Proxy Statement

Proposal 1: Election of Directors

Biographical Information

Ms. Cassotis has been the chief executive officer of the Allegheny County Airport Authority, which operates Pittsburgh International Airport and Allegheny County Airport since January 2015. Prior to that, Ms. Cassotis joined SH&E, Inc. in 1999, a global commercial aviation consulting firm, where she advised airports worldwide on strategy, business, and system planning. She went on to serve as managing officer for Airport Services for ICF-SH&E from 2007 to 2014, leading a global team of airport consultants. She also serves as a member of the board for the U.S. Travel Association, a member of the Board at the Federal Reserve Bank of Cleveland (Pittsburgh Branch) and a member of the International Aviation Women’s Association. Ms. Cassotis served as a director of EQT Corporation from October 2018 until July 2019.

Experience and Qualifications

Ms. Cassotis has demonstrated that she is a strong, decisive, and strategic leader. Her ability to identify the complex relationship between organizations and the competitive environments in which they operate has allowed her to position her business interests for the future while paying attention to immediate demands. Her substantial leadership roles within a highly-regulated, high-stakes industry provide valuable risk oversight experience, including with respect to cyber and technology, to the S&T Board. She is an innovative leader who has successfully directed necessary change through organizations to drive growth and deliver value which qualifies her to serve on the S&T Board.

Biographical Information

Ms. Doliveira has served as Executive Vice President of People & Culture at Sheetz, Inc, a privately-held family-owned and operated regional convenience retailer based in Altoona, Pennsylvania, since January 2023. In this role, she is responsible for strategic planning and execution of all people-centric initiatives, while also providing oversight of the company’s enterprise risk, legal and government affairs functions. Previously, she served as the Vice President of Human Resources (2008-2023), Interim Manager of Brand Strategy (2006-2008), and Manager of Internal Communications (2003-2008) for Sheetz. Ms. Doliveira was a practicing labor and employment attorney prior to joining Sheetz. She serves on the Pennsylvania Governor’s Early Learning Investment Commission, the Pennsylvania Chamber Board of Directors, and Sheetz Family Charities.

Experience and Qualifications

Ms. Doliveira’s experience at a large regional convenience retailer provides the Board with deep expertise in culture, large-scale workforce, leadership and compensation strategies that support organizational transformation. Her combination of executive and legal experience brings to the Board the ability to drive enterprise-wide initiatives and develop governance, compliance and enterprise risk management frameworks that balance innovation and risk mitigation in highly regulated, complex industries. Her extensive retail industry experience provides the Board with a unique strategic perspective and qualifies her to serve on the S&T Board.

S&T Bancorp, Inc. | 2026 Proxy Statement | 11

Proposal 1: Election of Directors

Biographical Information

Mr. Donnelly has been president of Indiana Printing and Publishing Company, Inc. since 1993. Mr. Donnelly has spent over 30 years working with the Indiana County Chamber of Commerce and the Indiana County Development Corporation in retaining and attracting many businesses in the Indiana, Pennsylvania area.

Experience and Qualifications

Mr. Donnelly’s deep experience in leading, managing and operating a local business provides the S&T Board with valuable insight into the issues addressing our local corporate and consumer borrowers. Mr. Donnelly’s experience in leading a business, related governance, and developing appropriate compensation for the executives and senior management of his company qualifies him to serve on the S&T Board.

Biographical Information

Mr. Grube has served as a Director since 1997 and was named Lead Independent Director of the S&T Board and the S&T Bank Board in 2025. Mr. Grube served as president of B.F.G. Manufacturing Service, Inc., which provides large volume plating, painting and powder coating services with facilities in Pennsylvania and New York from 1990 until his retirement in 2020. Mr. Grube’s career as an executive in the manufacturing industry includes financial and engineering experience. Mr. Grube also served as a director on the board of a privately held company that supplies compliance products for lending solutions.

Experience and Qualifications

Mr. Grube’s extensive experience working with small and medium-sized businesses provides the S&T Board with valuable experience regarding potential borrowers and customers, customer relations, lending issues and credit risk. Mr. Grube’s executive and board experience in the manufacturing sector and experience with financial institutions allow him to bring relevant insight regarding regulatory and financial compliance issues to the S&T Board.

12 | S&T Bancorp, Inc. | 2026 Proxy Statement

Proposal 1: Election of Directors

Biographical Information

Mr. Gurt has served as director of S&T since 2024. Mr. Gurt has been president of Milton Hershey School (“MHS”), one of the world’s largest private schools and which provides a home and schooling to children in social and financial need, since 2014. In October 2020, he also became the first president of Catherine Hershey Schools for Early Learning (“CHS”), a network of Early Childhood Education centers across Pennsylvania. CHS is a subsidiary of MHS with an initial investment of $350 million focused on serving children in need from birth to age five. Prior to this, he served in many leadership roles within MHS, including assistant to the president, vice president of administration, vice president of education and student life, and senior vice president and chief operating officer.

Experience and Qualifications

In Mr. Gurt’s current role as president of MHS and CHS, he is responsible for designing and executing strategy, and expanding the impact of the Milton Hershey School Trust. MHS is the sole beneficiary of the Milton Hershey School Trust, valued at more than $20 billion. The school’s trust is the sole proprietor of Hershey Entertainment & Resorts and controlling shareholder of The Hershey Company. Mr. Gurt has committed himself to serving his community through roles on the board and Commission for Accreditation at the Pennsylvania Association of Independent Schools. He has also served on several nonprofit boards throughout his career. Overall, Mr. Gurt’s extensive experience as a leader in business and education, and his community activism, fiduciary and risk management experience qualify him to serve on the S&T Board.

Biographical Information

Mr. Hieb served as the president and chief executive officer of DNB, the holding company for DNB First, N.A. since April 2016 until it was acquired by S&T in November 2019. He was a director of DNB since 2005 and a director of DNB First, N.A. since 2004. Mr. Hieb served as president and chief risk & credit officer of DNB from April 2011 to January 2016. Prior to that, Mr. Hieb served as president and chief operating officer of DNB from January 2005 to April 2011. Mr. Hieb has previously served on the board of directors for the Chester County Chamber of Business and Industry, the Chester County Historical Society, the Chester County Economic Development Council, the Chester County Chamber of Business and Industry and its Foundation, the Pennsylvania Bankers Association, the Housing Partnership of Chester County and Business Leadership Organized for Catholic Schools, and the West Chester University’s President Corporate Advisory Council.

Experience and Qualifications

Mr. Hieb has acquired considerable knowledge and experience during his 47 years in commercial banking including lending, credit administration, and wealth management. In addition, his background supervising DNB’s risk management function and operations during his career strengthens the Board’s collective qualifications, skills, and experience, and qualifies him to serve on the S&T Board.

S&T Bancorp, Inc. | 2026 Proxy Statement | 13

Proposal 1: Election of Directors

Biographical Information

Mr. McComish was named Chairperson of the S&T Board and the S&T Bank Board in 2025 and has been Chief Executive Officer of S&T and S&T Bank since August 24, 2021. Previously, he was senior executive vice president of consumer banking of TCF Bank, leading all consumer banking lines of business as well as business banking and wealth management from July 2018 to June 2021. Prior to TCF Bank, he served as president and chief executive officer of Scottrade Bank, the banking subsidiary of Scottrade Financial Services, Inc. from August 2015 to December 2017. In addition, he served as head of personal banking and then as chief operating officer for personal and commercial banking at BMO Harris Bank from December 2008 to July 2015. He began his career at Wachovia Bank, where he spent over 20 years in various regional and line of business leadership roles.

Experience and Qualifications

With more than 38 years of banking experience, including 23 years of senior management experience in his banking career, Mr. McComish’s strong leadership capabilities as a former chief executive officer, president and chief operating officer at other banking institutions and as senior executive vice president with a larger bank in the Midwest, provide the S&T Board with expertise that contributes to the strategic growth of S&T. As our Chief Executive Officer, Mr. McComish provides in-depth industry experience and insight in commercial banking, consumer banking, business banking and wealth management from a larger bank perspective. He is familiar with the impact of technology on banking, having served as the chief executive officer of a digital online bank, and brings to the S&T Board technology risk management experience. He also provides unique insight to the S&T Board regarding our day-to-day operations, risk and strategic initiatives, general trends in national and local banking, and issues regarding our financial results. Given his four years of leading the company as Chief Executive Officer, his solid performance and the performance of S&T since he became Chief Executive Officer , Mr. McComish is also well-positioned to serve as Chair, to capitalize on a deep understanding of S&T’s business and to identify issues that should be raised for consideration by the S&T Board and the S&T Bank Board.

14 | S&T Bancorp, Inc. | 2026 Proxy Statement

Proposal 1: Election of Directors

Biographical Information

Mr. Ramachandran has served as Global Vice President and Chief Information Officer of PPG Industries, Inc., a 140-year old Pittsburgh-based leading paints and coatings company, since 2021. From 2015 until joining PPG, Mr. Ramachandran served as Vice President, Information Technology, and Chief Information Officer of the largest division, of Jabil Inc., an American worldwide manufacturing services company. At Jabil, Inc., he led the creation of a fully cloud-based connected eco-system to make production more efficient and cost-effective. Prior to joining Jabil, Inc., Mr. Ramachandran progressed through information technology roles of increasing responsibility at Textron, Inc., a multi-industry company, where he was accountable for strategy development and operational elements of Textron, Inc.’s SAP center of excellence.

Experience and Qualifications

Mr. Ramachandran’s deep knowledge of cybersecurity and information technology provides the Board with valuable cyber and technology risk expertise, as well as a strong understanding of digital business strategies and emerging technology. Mr. Ramachandran’s extensive leadership experience at large, regulated companies, including his proven track record in scaling and transforming businesses, brings a diverse range of skills and knowledge that further contribute to an engaged and well-balanced Board. His work developing and leading diverse, high-performing teams across different industries and global companies also provides the Board with a unique perspective on people, process, adaptability and emotional intelligence.

Board Recommendation

S&T Bancorp, Inc. | 2026 Proxy Statement | 15

CORPORATE GOVERNANCE

Corporate Governance Guidelines

The Board has developed and adopted the Guidelines which reflect S&T’s commitment to following corporate governance best practices. The Guidelines are intended to promote the functioning of the Board and its committees and provide a common set of expectations as to how the Board should perform its functions. These Guidelines are not intended to modify or amend S&T’s Articles of Incorporation, as amended (the “Articles of Incorporation”), or By-laws. In the event of a discrepancy between these Guidelines and the Articles of Incorporation or the By-laws, the Articles of Incorporation and By-laws will always govern. The Guidelines are available on S&T’s website, www.stbancorp.com, under Governance.

Director Independence

The Board annually reviews and makes a determination as to the independence of its directors under the Nasdaq listing rules. In 2025, the Board also considered all direct and indirect transactions described under “Transactions with Related Parties” in determining whether a director is independent. Finally, the Board considered whether a director has any other material relationships with S&T and concluded that none of S&T’s directors, other than Mr. Antolik and Mr. McComish, has any such relationship that impairs the director’s independence. There were no other related party transactions other than those described under “Transactions with Related Parties” in this Proxy Statement. The Nominating Committee has the delegated responsibility to evaluate each director’s qualifications for independence for the Board and for the committees of the S&T Board. In accordance with the Nasdaq listing rules and interpretations, following review of the objective measures, the Nominating Committee and Board also evaluate on a subjective basis each director’s personal, familial and/or business relationship, regardless of dollar amount.

At a meeting held on January 28, 2026, the Board affirmatively determined the following nine directors and director nominees are independent under the Nasdaq listing rules: Mr. Adkins, Mr. Barsz, Ms. Cassotis, Ms. Doliveira, Mr. Donnelly, Mr. Grube, Mr. Gurt, Mr. Hieb, and Mr. Ramachandran. S&T provided financial services during 2025 to certain of S&T’s directors and to entities with which certain of S&T’s directors are affiliated. Affiliated entities include companies of which a director is, or was during 2025, an executive officer. We offer those services in the ordinary course of business on substantially the same terms and conditions, including price, as we provide to other similarly situated customers. The Board concluded that none of the subjective considerations impacted the independence of our directors.

Christine J. Toretti, who served as a director and independent Chair of the Board until her resignation on September 28, 2025 due to her appointment and confirmation as the United States Ambassador to Sweden, also qualified as independent during the period she served on the S&T Board. The Board also found Frank J. Palermo, Jr. who served as a director until May 13, 2025 when he did not stand for re-election, also qualified as independent during the period he served on the S&T Board. As discussed below, all members of the Compensation and Benefits Committee (the “Compensation Committee”) and the Nominating Committee are independent under the Nasdaq rules. In addition, the Board determined that each of the members of the Audit Committee is independent under applicable SEC and Nasdaq rules. The Board affirmatively determined that Mr. Antolik and Mr. McComish are the only non-independent directors as each is an executive officer of S&T. In making these determinations, the Board relied on the evaluation and recommendations made by the Nominating Committee. 

Board Structure; Board and Committee Meetings

There are currently 11 directors comprising the Board. The Board currently has established six standing committees: Audit, Compensation and Benefits, Credit Risk, Executive, Nominating and Corporate Governance, and Risk. Each Board Committee serves as a board committee of S&T Bank in addition to being a Board committee of S&T.

During 2025, the Board held six regular and two special board meetings, for a total of eight, with the following number of meetings held by the Board committees: Audit, eight; Compensation and Benefits, five; Credit Risk,

16 | S&T Bancorp, Inc. | 2026 Proxy Statement

Corporate Governance

four; Nominating and Corporate Governance, four; and Risk, four. The Executive Committee, which meets as often as it determines is necessary and appropriate, did not meet during 2025.

Each director of the Board attended at least 75% of the aggregate number of meetings of the Board and the committees on which he or she served during 2025. Independent members of the Board meet at least twice per year in regularly scheduled executive sessions without management present. The independent Chairperson of the Board or, when the position of Chairperson of the Board is not held by an independent director, the Lead Director, presides over all executive sessions. The Board has implemented a formal policy that strongly encourages director attendance at the annual meeting of shareholders. In 2025, all of S&T’s then serving on the Board directors attended the annual meeting of shareholders, except Frank J. Palermo, Jr. 

It is the Board’s policy not to mandate the separation of the offices of Chairperson of the Board and Chief Executive Officer (“CEO”). The Board believes it is in the best interests of S&T for the Board to make the determination from time to time as the circumstances warrant regarding the appropriate Board leadership structure. Pursuant to the Guidelines, when the position of Chairperson of the Board is not held by an independent director, a Lead Director, who is independent under Nasdaq and SEC rules, will be selected by the independent Board members to help ensure strong independent leadership on the Board. At a special meeting held on September 24, 2025, in connection with the resignation of the former Chairperson, Christine J. Toretti, the Board, including all members of the Nominating Committee, approved the creation of a Lead Independent Director position (“Lead Director”) on the Board and appointed the current CEO, Christopher J. McComish, to serve as the Chairperson of the Board. As a result, the Board appointed the current CEO of S&T, Christopher J. McComish, to serve as the Chairperson of the Board and appointed Jeffrey D. Grube, to serve as the Lead Director of the Board. The duties of the Lead Director are broad and substantive, promoting strong independent oversight over management and accountability to shareholders. The Board appointed Mr. McComish as Chairperson, given his four years of leading the company as CEO, his solid performance and the performance of S&T since he became CEO, all of which best position him to capitalize on a deep understanding of S&T’s business to identify the most critical business issues that should be raised for consideration by the Board. The Board believes these appointments and corporate governance changes are in the best interests of S&T and its shareholders.

The Lead Director serves as liaison between the CEO and the independent directors, supervises various board operations and governance, fostering an effective, engaged and independent board culture, and ensures the board fulfills its oversight responsibilities.

Pursuant to the Guidelines, the Lead Director has the following authority and responsibilities:

S&T Bancorp, Inc. | 2026 Proxy Statement | 17

Corporate Governance

When the position of Chairperson of the Board is not held by an independent director, the Chairperson of the Board shall have the following authority and responsibilities; provided that the following list is not an exclusive list of all duties of the Chairperson of the Board.

The Board believes that the current composition of the Board, the Board committees as presently constituted, and the leadership structure of the Board enable the Board to fulfill its role in overseeing and monitoring the management and operations of S&T and to protect the interests of S&T and its shareholders.

Director Succession Planning

One of our current directors, Jeffrey D. Grube, has reached the mandatory retirement age of 72 pursuant to S&T’s By-laws and Guidelines, and the Board anticipates that at least three other current directors will reach the mandatory retirement age over the next four years. In anticipation of these events, the Board and the Nominating Committee have been addressing Board composition and succession planning.

Mr. Grube, who was appointed to the Board in 1997, serves as Chair of the Credit Risk Committee and has served as Chair of the Compensation & Benefits Committee and as a member of the Audit Committee, Executive Committee and Risk Committee, was recently appointed as Lead Director, as discussed above, and has reached the mandatory retirement age. As part of its analysis of director succession, optimal Board composition and continuity of leadership, the Nominating and Governance Committee recommended, and our Board approved, a limited waiver of the mandatory retirement age for Mr. Grube simultaneously with the director nominations made by the Board in January 2026. The waiver is limited to the period ending with

18 | S&T Bancorp, Inc. | 2026 Proxy Statement

Corporate Governance

nominations for the 2028 annual meeting of shareholders, enabling Mr. Grube to serve on the Board through the 2029 annual meeting of shareholders, if elected. The waiver permits, but does not require, the Board to annually nominate Mr. Grube to serve on the Board and to continue to appoint him as the Lead Independent Director during such period.

Mr. Grube abstained from this vote. Mr. Grube has been nominated by the Board for election by shareholders at the Annual Meeting and is included in the Board nominees beginning on page 9.

The Board believes that it is in the best interests of S&T to waive the mandatory retirement age provision on a limited basis as described above. The Board does not currently intend to amend the By-laws or the Guidelines provisions with respect to the mandatory retirement age on a permanent basis.

The S&T Board’s Role in Risk Oversight

Role of the S&T Board

The S&T Board, with the assistance of the Risk Committee, oversees an enterprise-wide approach to risk management (“ERM”), designed to support the achievement of strategic goals, to improve long-term organizational performance and to enhance shareholder value. The Board’s oversight primarily focuses on material risks and any notable emerging themes to ensure S&T’s risk management is adequate. The chair of the Risk Committee, in collaboration with the Chairperson of the Board, helps ensure that the Board has appropriate discussions on risk topics. The Risk Committee is responsible for reviewing and recommending to the Board for approval certain risk appetites taking into account S&T’s structure, risk profile, complexity, activities, size, and other appropriate risk-related factors. The Risk Committee considers current risks, which include the respective timeframes reflected by those risks, emerging risks, and future threats.

The Risk Committee is responsible for overseeing S&T’s risk management activities and the effectiveness of its ERM framework. The Risk Committee is also responsible for monitoring our compliance risk with respect to regulatory and legal matters. The members of the Risk Committee are Peter R. Barsz, Christina A. Cassotis, Jeffrey D. Grube, William J. Hieb (Chairperson), and Bhaskar Ramachandran. Christine J. Toretti, a former director, served as a member of the Risk Committee until her resignation on September 28, 2025 due to her appointment and confirmation as the United States Ambassador to Sweden. Per the Risk Committee charter, the chairperson of the Risk Committee must satisfy the independence requirements established by the SEC, Nasdaq and any other governmental or regulatory body with authority over S&T. Mr. Hieb, Risk Committee Chairperson, meets such independence standards. The Risk Committee recommends to the Board the risk appetite or broad level of risk that is appropriate for S&T to accept. S&T’s risk appetite is an important piece of an effective ERM framework that reinforces risk culture and is a core instrument for better aligning overall corporate strategy, capital allocation, and risk.

Our Risk Committee’s primary purpose is to assist the Board in fulfilling its fiduciary responsibilities with respect to its oversight and assessment of S&T’s ERM framework, including among other things, the identification, assessment, measurement, monitoring, and management of the following major risk categories: Credit, Market, Liquidity, Operational, Information Technology and Security, Compliance/Regulatory, Legal, and Strategic. The Risk Committee meets quarterly or as often as it determines is necessary and appropriate. As with the other committees of the Board, the Risk Committee has the authority to consult with outside advisors as it deems necessary or appropriate to discharge its duties and responsibilities.

The Board, with the assistance of the Risk Committee, delegates the authority and responsibility for ensuring alignment of the risk appetite with the strategic objectives to the management-level Enterprise Risk Management Committee (the “ERM Committee”). The ERM Committee serves as the primary risk management forum for monitoring S&T’s risk exposures by reviewing key risk indicators or guidelines to proactively monitor both the level and direction of risk as well as key performance indicators to monitor progress toward achievement of strategic goals. By utilizing a comprehensive and standardized view of the nature and level of

S&T Bancorp, Inc. | 2026 Proxy Statement | 19

Corporate Governance

risk to which S&T is exposed and the interaction of the various risk components identified in its ERM program, S&T is better able to assess and manage its risk and react to uncertainties. S&T’s executive management-level committees, each of which is overseen by a Board committee, assists in this effort by helping S&T assess and manage issues, emerging risks and future threats identified across the organization and escalating them to the Board. 

The ERM Program utilizes a three lines of defense model to delegate responsibility for critical risk management processes across the business functions and operational areas, as well as risk management, compliance, and internal audit teams. S&T’s first line of defense consists of business areas and operational teams across S&T Bank. These areas and teams are responsible for identifying, assessing, mitigating, monitoring, and managing risk within their respective areas. S&T’s risk management functions represent the second line of defense. These functions are led by the Chief Risk Officer (“CRO”) and include a team consisting of a Director of Risk Management, Chief Appraisal Officer, Chief Compliance Officer, Chief Security Officer, Director of Credit Risk Review and Director of Operational Risk Management. S&T’s Audit and Advisory Department represents the third line of defense, which provides independent and objective assurance to senior management and the Board regarding first and second line risk management functions, internal controls, and governance processes.

The ERM Committee is comprised of members of S&T executive leadership, including the CRO, CEO, President, Chief Financial Officer (“CFO”), Chief Credit Officer, Commercial Banking Executive, Chief Human Resources Officer, Chief Operating Officer, Chief Audit Executive (“CAE”), Chief Consumer and Business Banking Officer, Director of Treasury Management, Banking Operations Division Manager, Director of Risk Management, Chief Compliance Officer, Chief Security Officer, Director of Credit Risk Review, Director of Operational Risk Management, and General Counsel. The ERM Committee meets at least quarterly to take the following actions prior to presentation to the Risk Committee: discuss the risk exposures of the enterprise, review changes to those exposures based on internal and external events, manage and mitigate such risks, and discuss significant policy changes, new products and services, and review ERM reports, including each of the corresponding risk management programs. The ERM Committee promotes proper risk management practices throughout S&T. A corporate policy approved by the Risk Committee governs the ERM Committee. The ERM Committee also operates pursuant to a written charter that is formally approved by the Risk Committee.

Role of the Board Committees

Pursuant to our Risk Committee charter, the CRO reports directly to the CEO, but has direct access to the Risk Committee, without impediment, and provides regular communication to the Risk Committee regarding risk management and regulatory compliance activities and other matters as the CRO determines necessary. The Risk Committee reviews and approves the appointment, replacement or dismissal of the CRO and oversees CRO succession planning.

The CRO, as the administrator of the ERM program, regularly meets with management, including the CEO, to discuss the primary areas of risk identified above as part of the ERM program. As necessary, the Risk Committee meets with the CRO to discuss and analyze risks to S&T without management present.

The Audit Committee is responsible for oversight of financial risk, including internal controls which encompasses disclosure controls and procedures, oversight of the registered public accounting firm independence and performance, oversight of the internal audit function, and oversight of all trust activities consistent with the Federal Deposit Insurance Corporation’s Statement of Principles of Trust Department Management. As part of the Audit Committee’s oversight of the internal audit function, they approve the appointment, replacement, or dismissal of the CAE. Pursuant to our Audit Committee charter, the CAE reports directly to the Audit Committee, with administrative oversight provided by the CEO. At least quarterly, the Audit Committee meets (including without Management present during executive sessions) with the CAE to review and assess risks identified by internal audit, the risk-based audit plan, sufficiency of resources (financial and staffing), departmental performance indicators, and the independence of the function within the organization. The Audit Committee meets twice quarterly or as often as it determines is necessary and appropriate.

20 | S&T Bancorp, Inc. | 2026 Proxy Statement

Corporate Governance

The Compensation and Benefits Committee is responsible for assessing and mitigating risks associated with S&T’s human capital and compensation practices, both with respect to S&T’s NEOs (as further described in the Compensation Discussion and Analysis (“CD&A”) section of this Proxy Statement) and its employees generally. The Compensation Committee reviews the incentive compensation arrangements for S&T’s NEOs with the CRO at least annually to discuss and evaluate the risk posed to S&T by its employee compensation plans and to ensure that the compensation arrangements do not encourage the NEOs to take unnecessary and excessive risks that threaten the value of S&T. The Compensation Committee meets quarterly or as often as it determines is necessary and appropriate.

Our Credit Risk Committee is responsible for reviewing the credit administration risk management practices and reporting; the performance of the independent credit risk review function and its assessment of the management of credit risk arising from the lending and lending-related functions of S&T; the review of commercial lending activity, including portfolio reviews; the credit policy approval; and providing guidance on pertinent credit risk matters including loan-related strategies. The members of the Credit Risk Committee are Lewis W. Adkins, Michael J. Donnelly, Jeffrey D. Grube (Chairperson), Peter G. Gurt, and William J. Hieb. The Credit Risk Committee meets quarterly or as often as it determines is necessary and appropriate. The Credit Risk Committee reviews and approves the appointment, replacement, or dismissal of the Director of Credit Risk Review and at least annually reviews with the Director of Credit Risk Review the plans, activities, staffing and organizational structure of the credit risk review function. At least quarterly or as needed, the Credit Risk Committee meets with the Director of Credit Risk Review to discuss and analyze credit risks to S&T without management present.

The Executive Committee is responsible for exercising the authority to act on behalf of the Board between meetings of the Board to the fullest extent permitted by law. The Executive Committee meets as often as it determines is necessary and appropriate. Peter R. Barsz, Christina A. Cassotis, Michael J. Donnelly, Jeffrey D. Grube, William J. Hieb, and Christopher J. McComish serve as members of the Executive Committee. Christine J. Toretti, a former director, served on the Executive Committee as Chair, until her resignation on September 28, 2025.

Employee Compensation Policies and Managing Risk

We believe our approach to goal setting, setting of targets with payouts at multiple levels of performance, and evaluation of performance results assists in mitigating excessive risk taking that could harm our value or reward poor judgment by our executives. We believe that several features of our compensation policies and programs reflect sound risk management practices, such as basing incentive awards on the achievement of predetermined earnings per share (“EPS”), pre-provision net revenue and non-performing asset goals, all audited numbers, and granting restricted awards subject to a three year tiered time or three year cliff performance vesting that serves the additional purpose of encouraging senior management to make current decisions that promote long-term growth, promoting retention of senior management and requiring senior management to meet stock ownership guidelines. All awards granted under S&T Bancorp, Inc.’s 2021 Incentive Plan (the “2021 Incentive Plan”) were subject to Compensation Committee review and approval based upon corporate and/or individual performance.

The incentive plan for senior management, as described in the CD&A section below, contains a “Minimum Gateway Requirement” (other than for time-based awards) and a “Shareholder Protection Feature,” which provide that awards will not be made unless S&T achieves a Return on Average Equity of at least 5% and maintains well capitalized capital ratio requirements, as established by applicable regulatory authorities, respectively. We believe we have allocated our compensation among base salary and short and long-term compensation target opportunities in such a way as to not encourage excessive risk-taking. The Compensation Committee also reviews compensation and benefits plans affecting employees in addition to those applicable to executive officers. Based on the review by the Compensation Committee, the S&T Board determined that it is not reasonably likely that S&T’s compensation and benefit plans would have a material adverse effect on S&T.

S&T Bancorp, Inc. | 2026 Proxy Statement | 21

Corporate Governance

Audit Committee

The Audit Committee is established in accordance with Section 3(a)(58)(A) of the Exchange Act. The members of the Audit Committee are Peter R. Barsz (Chairperson), Christina A. Cassotis, Jeffrey D. Grube, and William J. Hieb. All members meet the independence standards for audit committees established by the SEC and Nasdaq. Frank J. Palermo, a former director who served as the Chair of the Audit Committee until May 13, 2025 when he did not stand for re-election, was also independent during the time of his service.

A written charter approved by the Board governs the Audit Committee and complies with current Nasdaq Rules relating to charters and corporate governance. The Audit Committee reviews the adequacy of this charter annually and recommends any proposed changes to the Board. A copy of the charter is included on S&T’s website www.stbancorp.com, under Governance. The Audit Committee has provided information regarding the functions performed by the Audit Committee and its membership in the “Report of the Audit Committee,” included in this Proxy Statement on page 68.

The Board has determined that Peter R. Barsz, Chair of the Audit Committee, CPA, and William J. Hieb each qualify as an “audit committee financial expert” as defined in regulations issued pursuant to the Sarbanes-Oxley Act of 2002. The Board also determined that Frank J. Palermo, CPA, a former director and Chair of the Audit Committee, qualified as an “audit committee financial expert” until the expiration of his term immediately following the 2025 annual meeting of shareholders.

The Audit Committee annually reviews the independent registered public accounting firm’s performance and independence in deciding whether to retain the firm or engage a different independent registered public accounting firm. As part of this review, the Audit Committee considers, among other things, the following:

The Audit Committee has the authority to consult with outside advisors as it deems necessary or appropriate to discharge its duties and responsibilities.

Compensation and Benefits Committee

The members of the Compensation Committee are Lewis W. Adkins, Jr., Christina A. Cassotis (Chairperson), Michael J. Donnelly, Jeffrey D. Grube, Peter G. Gurt, and Bhaskar Ramachandran. The Compensation

22 | S&T Bancorp, Inc. | 2026 Proxy Statement

Corporate Governance

Committee’s primary function is to recommend to the Board action on executive compensation and compensation and benefit changes brought to it by management.

A written charter approved by the Board governs the Compensation Committee and complies with current Nasdaq Rules relating to charters and corporate governance. The Compensation Committee reviews the adequacy of this charter annually and recommends any proposed changes to the S&T Board. A copy of the charter is included on S&T’s website www.stbancorp.com, under Governance. The Compensation Committee is comprised entirely of independent board members, as defined by Nasdaq listing standards.

The Compensation Committee is responsible for our stated compensation strategies, goals and purposes, ensuring that there is a strong link between the economic interests of management and shareholders; that members of management are rewarded appropriately for their contributions to company growth and profitability; that the executive compensation strategy supports organization objectives and shareholder interests; and that human capital programs and policies, including with respect to management development, succession planning and inclusion initiatives are effective. The Compensation Committee must provide clear direction to management to ensure that its policies and procedures are carried out in a manner that achieves balance and is consistent with safety and soundness. It approves any material exceptions or adjustments to the incentive compensation arrangements established for senior management and carefully considers and monitors the effects of any approved exceptions or adjustments. In support of the Compensation Committee’s responsibilities, S&T has an Incentive Compensation Steering Committee (“Steering Committee”), which operates under a formal management committee charter and whose members consist of the CEO, the President, the CFO, the CRO, Chief Human Resource Officer, the Chief Operating Officer and any other officer that the Compensation Committee deems appropriate. The Steering Committee reviews all incentive plans to ensure that they are equitable across all business lines, tie to organizational goals, do not encourage excessive risk-taking and are not designed to encourage misconduct or illegal behavior. As part of the Steering Committee’s responsibilities, it applies the safety and soundness guidelines established in our formal Incentive Compensation Arrangements policy.

The Compensation Committee receives and reviews, on an annual or more frequent basis, an assessment by management, with input from risk management personnel, of the effectiveness of the design and operation of the organization’s incentive compensation system in providing appropriate risk-taking incentives. It also reviews periodic reports of incentive compensation awards and payments relative to risk outcomes. It ensures that the incentive compensation arrangements for S&T do not encourage employees to take risks that are beyond S&T’s ability to manage effectively. It also performs other related duties as set forth in its written charter.

The process, policies and specific determinations of the Compensation Committee with respect to compensation of our NEOs for fiscal year 2025, including management’s role in such process, are described in greater detail in the CD&A section of this Proxy Statement.

The Compensation and Benefits Committee Report is on page 47 of this Proxy Statement.

The Compensation Committee has the authority to consult with outside advisors as it deems necessary or appropriate to discharge its duties and responsibilities.

Nominating and Corporate Governance Committee

The members of the Nominating Committee are Lewis W. Adkins, Jr., Michael J. Donnelly (Chairperson), Peter G. Gurt, and Bhaskar Ramachandran.

The Nominating Committee’s functions are to assist the Board in annually reviewing the qualifications and independence of the members of the Board and its various committees as well as the composition and structure of the Board; to review and make recommendations to the Board as to its committee structure, functions and

S&T Bancorp, Inc. | 2026 Proxy Statement | 23

Corporate Governance

composition on a periodic basis; to oversee the annual assessment of the performance of the Board, its committees and its directors, including whether its committees are functioning effectively; to recommend director nominees to the Board to submit for election by shareholders; and to provide guidance to the Board on corporate governance issues. Prior to beginning the annual assessment of the Board and its committees, the Nominating Committee considers possible enhancements to the process to ensure continued effectiveness. Any feedback on the assessment process from the prior year is incorporated. Each year, the Nominating Committee oversees a robust assessment process that includes three separate assessments, a Board self-assessment, a committee self-assessment that is specific to each committee and an individual director self-assessment. In connection with the 2025 assessment, the Nominating Committee and the Board agreed to engage a third party to facilitate the assessment. The results of the Board and committee self-assessments are reviewed by the Chair of the Nominating Committee, the Lead Independent Director and the Board Chairperson, then shared, reviewed and discussed with the Board. To encourage candor, the individual director self-assessments are shared only with the Chair of the Nominating Committee, the Lead Independent Director and the Board Chairperson. The Chair of the Nominating Committee, the Lead Independent Director and the Board Chairperson, individually or together, may hold one-on-one discussions with individual directors to further discuss the Board, committee and individual director self-assessments. The self-assessments pay particular attention to the Board’s oversight of S&T’s risk management framework, Board refreshment, the structure of the Board and its committees and the Board’s ability to take actions and make decisions efficiently and independently from management.

In addition, the Nominating Committee reviews all transactions with related parties, as further described on page 64 of this Proxy Statement. The Nominating Committee oversees the director onboarding process and the continuing education programs for all directors. To assist in remaining current with Board duties and committee responsibilities, the Board regularly has educational sessions with internal and external resources during Board meetings and participates in a third-party educational program designed specifically for bank directors. This program offers access to online video training series, a wide range of in-person conferences, periodic hard copy and digital magazines, and peer-based and webinar educational programs on corporate governance, risk management, committee duties, board leadership and industry developments. Various other educational opportunities and sources are also provided to the Board.

A written charter approved by the Board governs the Nominating Committee and complies with current Nasdaq Rules relating to charters and corporate governance. The Nominating Committee reviews and reassesses the adequacy of this charter annually and recommends any proposed changes to the Board. A copy of the charter is included on S&T’s website www.stbancorp.com, under Governance. The Nominating Committee is comprised entirely of independent board members, as defined by Nasdaq listing standards. Mr. Palermo, a former director who served on the Nominating Committee until May 13, 2025 when he did not stand for re-election, was also independent during the time of his service.

The Nominating Committee has the authority to consult with outside advisors as it deems necessary or appropriate to discharge its duties and responsibilities.

Director Qualifications and Nominations

The Nominating Committee has adopted, and the Board has ratified, a corporate policy for identifying and evaluating candidates for membership on the Board. The Nominating Committee identifies potential candidates based on suggestions from directors, officers of S&T, and S&T shareholders. An S&T shareholder may make a director nomination in accordance with Section 202 of S&T’s By-laws and applicable law. The procedure under Section 105 of the By-laws provides that a notice relating to the nomination must be timely given in writing to the Secretary of S&T, at 800 Philadelphia Street, Indiana, Pennsylvania 15701, prior to the annual meeting. To be timely, the notice must be delivered not earlier than the close of business on the 120th day (January 12, 2027), nor later than the close of business on the 90th day (February 11, 2027), prior to the first anniversary of the preceding year’s annual meeting (May 12, 2027), unless the date of the annual meeting is more than 30 days before or more than 60 days after such anniversary date, in which case we will notify you of

24 | S&T Bancorp, Inc. | 2026 Proxy Statement

Corporate Governance

the new deadlines. Among other requirements, such notice must be accompanied by the nominee’s written consent to be named in the applicable proxy statement and contain information relating to the business experience and background of the nominee and the nominee’s holdings of S&T Common Stock and information with respect to the nominating shareholder. There are no differences in the manner in which the Nominating Committee considers and evaluates candidates for membership on the Board based on whether such candidate is recommended by a shareholder, the Nominating Committee, or by any other source.

In evaluating and selecting nominees to the Board, the Nominating Committee takes into account all factors and criteria it considers appropriate, which includes but is not limited to the following: high personal and professional integrity; sound independent judgment and exceptional ability; business experience; collaborative approach to engagement and oversight; inquisitive and objective perspective; area of residence in relationship to S&T’s geographic market; other directorship experience that would be beneficial to the Board and management of S&T; diversity of experience relative to that of other S&T directors; diversity of age, gender, minority status, and level and type of education; whether the candidate will be effective in serving the long-term interests of S&T’s shareholders; whether the candidate has sufficient time and energy to devote to the affairs of S&T; whether the candidate possesses a willingness to challenge and stimulate management and the ability to work as part of a team; whether the candidate meets the independence requirements of the Nasdaq listing standards; whether the candidate is free from conflicts of interest with S&T; whether the candidate has any other skills and qualifications identified from time by the Board; and any other factors related to the ability and willingness of a new director to serve or an existing director to continue his or her service.

The Nominating Committee may engage a third-party search firm to assist it in identifying director candidates who meet the above-identified criteria and did so in 2025. S&T did not receive any timely shareholder nominations for a director for consideration for this Annual Meeting.

Shareholder Communications with Directors

Shareholders who desire to communicate with the Board or a specific director should send any communication, in writing, to S&T Bancorp, Inc., 800 Philadelphia Street, Indiana, Pennsylvania 15701, Attention: Secretary. Any such communication should state the number of shares beneficially owned by the shareholder. S&T’s Secretary will initially review all communications received in accordance with the Shareholders Communication Policy adopted by the Board. The Secretary will relay all such communications to the appropriate director or directors on a periodic basis unless the Secretary determines that the communication does not relate to the business or affairs of S&T or the functioning or constitution of the Board or any of its committees; relates to routine or insignificant matters that do not warrant the attention of the Board; is an advertisement or other commercial solicitation or communication; is frivolous or offensive; or is otherwise not appropriate for delivery to directors. The director or directors who receive any such communication will have discretion to determine whether the subject matter of the communication should be brought to the attention of the full Board or one or more of its committees and whether any response to the person sending the communication is appropriate. Any such response will be made through S&T’s management and only in accordance with S&T’s policies and procedures and applicable laws and regulations relating to the disclosure of information. If the Secretary believes the communication may be a complaint relating to any questionable accounting, internal accounting controls or auditing matter (“Covered Matter”), the Covered Matter will be handled in accordance with S&T’s Complaints Regarding Accounting, Internal Accounting Controls or Auditing Matters Policy (“Whistleblower Policy”). A copy of the Whistleblower Policy is included on S&T’s website www.stbancorp.com, under Governance.

Code of Conduct and Ethics

The S&T Board has adopted a General Code of Conduct for directors, officers, and employees and has further adopted a Code of Conduct for the CEO and CFO (the “Senior Officer Code”, which contains additional provisions separate from the General Code of Conduct applicable to our CEO and CFO). Both the General Code of Conduct and the Senior Officer Code are posted on S&T’s website www.stbancorp.com, under Governance. The General Code of Conduct addresses the professional, honest and candid conduct of each director, officer

S&T Bancorp, Inc. | 2026 Proxy Statement | 25

Corporate Governance

and employee; conflicts of interest, disclosure process, and compliance with laws, rules and regulations (including insider trading laws); corporate opportunities, confidentiality, self-dealing and fair dealing; and protection and proper use of company assets. It also encourages reporting any illegal or unethical behavior. The Senior Officer Code addresses the CEO and CFOs duty to report certain significant deficiencies in S&T’s internal control over financial reporting or fraud involving financial reporting, disclosures, or internal control over financial reporting and other violations of laws. A waiver of the General Code of Conduct for an executive officer or director of S&T (or a waiver of the Senior Officer Code for the CEO or CFO) may be made only by the Board and must be promptly disclosed as required by SEC or Nasdaq rules. S&T will disclose any such waivers, as well as any amendments to the General Code of Conduct or the Senior Officer Code, on S&T’s website. Shareholders may obtain a printed copy of the Code of Conduct or the Senior Officer Code by contacting the Secretary at the address previously provided.

26 | S&T Bancorp, Inc. | 2026 Proxy Statement

DIRECTOR COMPENSATION

The Nominating Committee annually reviews S&T’s director compensation and makes recommendations to the Board. S&T’s director compensation is designed to align the S&T Board with its shareholders and to attract, motivate and retain high-performing members critical to S&T’s success. A directors’ compensation analysis including a peer comparison is completed annually. The objective is to evaluate director compensation against S&T’s peer group to ensure S&T’s compensation practices for its directors are consistent with banks its size and within similar markets. S&T uses a combination of cash and restricted stock units to attract and retain qualified candidates to serve on the Board. Restricted stock unit grants are intended to align directors’ interests with those of S&T’s shareholders. In connection with a compensation analysis completed by the Board in 2025, the Board revised the cash retainer payment schedule, effective May 2026, from one annual lump sum payment to quarterly pro rata payments, consistent with continuing service on the Board during the year.

In 2025, our non-employee directors received compensation for serving on the Board and attending Board and committee meetings in the amounts described below. Employee members of the Board receive no additional compensation for participation on the Board. We reimbursed various directors for amounts expended for traveling to our meetings and to educational seminars. We determined these amounts were consistent with our guidelines and thus are not included in the 2025 Director Compensation table.

28 | S&T Bancorp, Inc. | 2026 Proxy Statement

Director Compensation

The following table provides information concerning compensation paid by S&T to its non-employee directors during 2025.

Director Compensation Table for Fiscal Year 2025

Directors’ Stock Ownership

The Board had previously adopted stock ownership guidelines for the directors of S&T, which required each director to own at least $100,000 in market value of Common Stock within one year of being elected to the Board in order to be nominated for reelection as a continuing director candidate for a second or third term of service. To be nominated for reelection as a continuing member of the Board for a fourth, or more, term of service, such continuing director candidate must own at least $250,000 in market value of the Common Stock. Each of our directors satisfied the stock ownership guidelines as of January 28, 2026, the date of nomination.

S&T Bancorp, Inc. | 2026 Proxy Statement | 29

Director Compensation

Effective immediately following the nomination of directors for the May 2026 – May 2027 term during its January 28, 2026 meeting, the Board approved revised stock ownership guidelines to better align with industry practice. The Board reviewed information from Aon, the independent compensation consultant, when making its decision to revise the stock ownership guidelines. Under the revised guidelines, a director must own four times the annual cash retainer by the later of five years from January 28, 2026, the date the Board adopted the revised guidelines, or five years from the date of the director’s initial appointment to the Board.

30 | S&T Bancorp, Inc. | 2026 Proxy Statement

PROPOSAL 2: RATIFICATION OF THE SELECTION OF INDEPENDENT REGISTERED

PUBLIC ACCOUNTING FIRM FOR FISCAL YEAR 2026

The Audit Committee of the S&T Board appointed the firm of Ernst & Young LLP (Ernst & Young) as its independent registered public accounting firm (“Independent Accountants”), to audit and report on S&T’s financial statements for the fiscal year ending December 31, 2026. The S&T Board now recommends that S&T’s shareholders ratify this appointment.

We are not required to have the shareholders ratify the selection of Ernst & Young as our independent registered public accounting firm. We are doing so because we believe it is a matter of good corporate practice. If the shareholders do not ratify the selection, the Audit Committee will reconsider whether or not to retain Ernst & Young but may nevertheless decide to continue to retain such independent registered public accounting firm. Even if the selection is ratified, the Audit Committee, in its discretion, may change the appointment at any time during the year if it determines that such change would be in the best interests of S&T and its shareholders.

Ernst & Young has no direct or indirect financial interest in S&T or in any of its subsidiaries, nor has it had any connection with S&T or any of its subsidiaries in the capacity of promoter, underwriter, voting trustee, director, officer, or employee. Representatives of Ernst & Young are expected to be present at the virtual Annual Meeting and will be afforded an opportunity to make a statement if they desire to do so. It is also expected they will be available to respond to appropriate questions.

Fees Paid to Independent Registered Public Accounting Firm

The financial statements of S&T are audited annually by an independent registered public accounting firm. For the fiscal years ended December 31, 2025 and December 31, 2024, the audit was performed by Ernst & Young. Fees for professional services provided by Ernst & Young in each of the last two fiscal years are summarized below:

“Audit Fees” for 2025 and 2024 include fees for audit services associated with the annual audit, the reviews of S&T’s quarterly reports on Form 10-Q, and other documents filed with the SEC, accounting consultations, comfort letters, and consents.

“Audit-Related Fees” for 2025 and 2024 include fees billed for U.S. Department of Housing and Urban Development compliance procedures.

“Tax Fees” include fees for tax compliance work for the Wealth Management division for client fiduciary tax returns performed in 2025 and 2024.

There were no “All Other Fees” for 2025 and 2024.

Pre-Approval Policies and Procedures

The Audit Committee is responsible for the approval of all services performed by S&T’s independent registered accounting firm. All services provided by Ernst & Young in 2025 were pre-approved by the Audit Committee. The Audit Committee is required to pre-approve all audit and non-audit services performed by the Independent

S&T Bancorp, Inc. | 2026 Proxy Statement | 31

Proposal 2: Ratification of the Selection of Independent Registered

Public Accounting Firm For Fiscal Year 2026

Accountants to assure that the provision of such services does not impair the Independent Accountant’s independence. In addition, any proposed services exceeding pre-approved cost levels will require specific pre-approval by the Audit Committee. The Audit Committee may delegate pre-approval authority to one or more of its members. The member or members to whom such authority is delegated will report any pre-approval decisions to the Audit Committee at its next scheduled meeting for ratification. The Audit Committee does not delegate its responsibilities to pre-approve services performed by the Independent Accountants to management.

Board Recommendation

THE S&T BOARD RECOMMENDS A VOTE “FOR” RATIFICATION OF THE SELECTION OF ERNST & YOUNG LLP AS S&T’s INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR FISCAL YEAR 2026.

32 | S&T Bancorp, Inc. | 2026 Proxy Statement

PROPOSAL 3: ADVISORY VOTE TO APPROVE COMPENSATION

OF S&T’S NAMED EXECUTIVE OFFICERS

S&T believes that our overall executive compensation program, as described in the “Compensation Discussion and Analysis” section elsewhere in this Proxy Statement, is designed to pay for performance and directly aligns the interest of our executive officers with the long-term interests of our shareholders.

As required by Section 14A of the Exchange Act, S&T is providing its shareholders a vote to approve, on a non-binding advisory basis, the compensation of our NEOs as disclosed in this Proxy Statement in accordance with the SEC’s rules. This vote is not intended to address any specific item of compensation or the compensation of any particular officer, but rather the overall compensation of our NEOs and our compensation philosophy, policies, and practices. Pursuant to Section 14A of the Exchange Act, the Board recommended, and the shareholders subsequently approved on an advisory basis at the 2025 annual meeting of shareholders, that this advisory proposal on executive compensation be submitted to shareholders annually. Accordingly, S&T intends to continue holding an advisory vote on compensation of NEOs every year. S&T’s shareholders will again be asked to approve the frequency of the advisory vote on executive compensation at S&T’s 2030 annual meeting.

Accordingly, S&T is presenting the following advisory proposal, commonly known as the “say-on-pay proposal,” for shareholder approval:

“Resolved, that the shareholders hereby approve, on a non-binding basis, the compensation of our Named Executive Officers as disclosed in this Proxy Statement pursuant to Item 402 of Regulation S-K, which disclosure includes the compensation discussion and analysis, the compensation tables and all related material.”

Because your vote is advisory, it will not be binding upon the Board. In the event this proposal is not approved by our shareholders, it will not be construed as overruling a decision by the Board or the Compensation Committee, nor create or imply any additional fiduciary duty by the Board or our Compensation Committee, nor will it be construed to restrict or limit the ability of our shareholders to make proposals for inclusion in proxy materials related to executive compensation. Notwithstanding the foregoing, the Board and the Compensation Committee will consider the non-binding vote of our shareholders on this proposal when reviewing compensation policies and practices in the future.

Board Recommendation

THE S&T BOARD RECOMMENDS A VOTE “FOR” THE APPROVAL OF THE COMPENSATION OF S&T’s NAMED EXECUTIVE OFFICERS.

S&T Bancorp, Inc. | 2026 Proxy Statement | 33

EXECUTIVE OFFICERS OF THE REGISTRANT

Each executive officer of S&T holds office for the current year for which he or she was elected or appointed by the Board unless he or she resigns, becomes disqualified or is removed at the discretion of the S&T Board. The current executive officers of S&T and S&T Bank are:

34 | S&T Bancorp, Inc. | 2026 Proxy Statement

COMPENSATION DISCUSSION AND ANALYSIS

INTRODUCTION

We provide the following overview of S&T’s executive compensation principles, specific executive compensation programs, and pay decisions that were made by the Compensation Committee in 2025. In addition, we describe the process by which we arrive at specific compensation policies and decisions involving program design and pay for S&T’s NEOs, who are listed below.

EXECUTIVE SUMMARY

Key Business and Financial Highlights

As reported in S&T’s Form 10-K for the year ended December 31, 2025, we are pleased to report:

Key 2025 Compensation Decisions

For 2025, the Compensation Committee evaluated and approved the following adjustments and awards for our NEOs:

S&T Bancorp, Inc. | 2026 Proxy Statement | 35

Compensation Discussion and Analysis

SAY ON PAY AND SHAREHOLDER ENGAGEMENT

S&T is required to provide a separate non-binding shareholder advisory vote on the compensation of S&T’s NEOs. At the 2025 annual meeting of shareholders, the holders of 26,335,649 shares of Common Stock, or 94% of the shares voting on the proposal, voted to approve the non-binding, advisory proposal on the compensation of S&T’s executive officers.

The Compensation Committee believes the results of this vote demonstrate the strong support for S&T’s executive compensation policies and practices among shareholders. The Compensation Committee expects to continue to adhere to the compensation policies, principles and programs described below in future years and will continue to consider these non-binding advisory results on our compensation programs, among other factors.

36 | S&T Bancorp, Inc. | 2026 Proxy Statement

Compensation Discussion and Analysis

OVERVIEW OF THE COMPENSATION PROGRAM, POLICIES AND PROCESS

Executive Compensation Philosophy and Practices

S&T designs its management compensation programs and policies to optimize their alignment with S&T’s strategic direction and business environment within which it must create value for shareholders and focus on pay for performance. Listed below are some of S&T’s primary program objectives, practices, and policies.

S&T Bancorp, Inc. | 2026 Proxy Statement | 37

Compensation Discussion and Analysis

Compensation Approval Process

Our Compensation Committee engages with management and an independent compensation consultant as a part of its processes – the role of each and the overall compensation approval process are described in greater detail below.

38 | S&T Bancorp, Inc. | 2026 Proxy Statement

Compensation Discussion and Analysis

Use of Competitive Data

The Compensation Committee reviews comparisons of the compensation programs established by peer banks for executives having similar responsibilities to S&T’s executives to obtain a general understanding of current market practices to assist in evaluating S&T’s compensation program. In 2024, and refreshed in 2025, the Compensation Committee engaged Aon to advise on the appropriateness of the banks in the peer group considering S&T’s current status and common practices among peer banking organizations for defining peer groups for executive compensation review purposes. In 2025 the Compensation Committee reviewed and agreed with Aon’s recommendations and selected the following peer group for its 2025 executive compensation decisions based on similar size and scope to S&T and operating both inside and outside S&T’s geographic market (collectively, the “Peer Banks”):

During 2025, five Peer Banks were removed due to pending acquisitions and were replaced with others in a similar asset size as indicated by an asterisk. The Peer Banks were used by Aon to analyze the total direct compensation for S&T’s executives for 2025. The Compensation Committee used the companies in the S&P 600 Bank Industry Index as of January 1 of the plan year, including the 2025 plan year (the “Performance Peer Group”), for comparing S&T’s relative performance for the applicable year’s performance based units.

Total Direct Compensation Position

S&T’s target pay mix is built on competitive base salaries, with generally moderate annual and long-term incentive targets. The moderate positioning of annual incentives and long-term incentives reflects our commitment to introducing pay program modifications that are both sensitive to S&T’s proactive risk management culture while, at the same time, responding appropriately to the importance of retaining a strong and committed leadership team at S&T. The Compensation Committee reviews this posture periodically with the help of outside advisors.

For NEOs, the Compensation Committee reviews a number of analyses of compensation practices to help facilitate its executive compensation decisions. These include:

S&T Bancorp, Inc. | 2026 Proxy Statement | 39

Compensation Discussion and Analysis

COMPONENTS OF THE COMPENSATION PROGRAM

The Compensation Committee continues to support a pay program with five major components to help guide compensation decisions:

A detailed review of each of the above compensation components and the 2025 decisions and payouts is provided in the sections below.

Base Salary

As described above, the purpose of base salary is to provide competitive and fair base compensation that recognizes the executives’ roles, responsibilities, contributions, experiences, and performance. The Compensation Committee independently decides the compensation that S&T will pay the CEO and President and, for the remaining executive officers, the CEO makes recommendations to the Compensation Committee, which reviews, approves or adjusts the recommendations. Each executive’s individual pay reflects individual experience, expertise, performance, and contributions in the role.

40 | S&T Bancorp, Inc. | 2026 Proxy Statement

Compensation Discussion and Analysis

2025 Base Salary Amounts

When appropriate, the Compensation Committee increases base salaries both to ensure consistency with market competitive practices and to recognize the critical value of each senior executive’s management of S&T. The following table summarizes the 2025 base salaries for each of our NEOs.

Management Incentive Plan Awards

For 2025, we adopted the 2025 MIP, an annual cash incentive award with a target equal to a set percentage of base salary for each of our NEOs.

The following formula is used to determine MIP award payouts:

To further strengthen the linkage between the MIP award, risk management, and shareholder value creation, the MIP contains a “Shareholder Protection Feature” in which payouts will not occur for any plan year if S&T falls below “well capitalized” capital ratio requirements established by regulatory authorities, determined as of and up to the date that any payment would ordinarily occur pursuant to the MIP’s provisions. In addition to the Shareholder Protection Feature of the MIP, the MIP is operational only if S&T achieves Return on Average Equity (“ROAE”) for the plan year of at least 5% (the “Minimum Gateway Requirement”). The Compensation Committee believes that these features, coupled with the claw-back requirements and the use of multiple performance measures, provide for substantial protection against excessive or unnecessary risk-taking by any plan participant.

Target Bonus Percentages

The following table shows the target percentage of base salary for each NEO. The Compensation Committee, considering Aon’s advice, continued to omit the individual performance component and set S&T’s corporate performance factor as the only performance component of the 2025 MIP for the NEOs and other Section 16 officers. We believe that the 2025 MIP’s targets are consistent with our philosophy of providing our NEOs the opportunity for reasonable annual incentives and designing a larger portion of compensation as “at-risk” to reflect their roles within our organization. We also believe the corporate performance factor appropriately recognizes the importance of S&T achieving key financial performance goals.

S&T Bancorp, Inc. | 2026 Proxy Statement | 41

Compensation Discussion and Analysis

Corporate Performance Factor

For the 2025 fiscal year, we continued with certain aspects of our incentive compensation program to ensure S&T’s ability to recruit and retain top talent while further increasing the percentage of our NEO’s total direct compensation that is at-risk and tied to S&T’s performance metrics.

Specifically, the annual MIP continues in 2025 with the metrics from 2024 for the performance factor. We retained Earnings per Share (EPS) as a metric weighted at 60% and also utilized Pre-Provision Net Revenue/Average Assets (“PPNR”)⁽¹⁾ (weighted at 20%) and Non-performing Assets/Loans+Other Real Estate Owned (20%). The PPNR⁽¹⁾ ratio is incorporated to have a profitability measure which is neutral to the impact of asset quality and taxes. There is no individual performance factor included in the MIP calculation for NEO’s and the award and payout is based solely on company performance.

The actual earnings opportunity was based on the performance level achieved relative to the performance ranges shown in the table below with a target EPS equal to $3.20; PPNR⁽¹⁾ of 1.69%; and asset quality of 0.39%. “Allocated Target” equals the participant’s MIP incentive target multiplied by the weighting for each performance category (i.e., 60% for EPS, 20% for PPNR⁽¹⁾ and 20% for asset quality).

Note: Linear interpolation is utilized to determine awards between Threshold and Target and Target and Maximum

Individual Performance Factor

Participants other than the NEOs, Section 16 officers, as well as several other key positions have an Individual Performance Factor with multiple individual goals against which individual performance was evaluated. The framework for establishing these goals was based largely on execution of elements of S&T’s strategic plan, including activities centered around multi-faceted growth, profit improvement, operational effectiveness, corporate culture, effective brand and enterprise risk management (i.e., balanced risk and reward).

Summary of 2025 MIP Payouts

The Payout Level Percentage for 2025 MIP Payouts to the NEOs was 119% of target, determined as follows:

MIP results

42 | S&T Bancorp, Inc. | 2026 Proxy Statement

Compensation Discussion and Analysis

Based on achieving 119% of the Target Performance Level, the Compensation Committee approved the following cash awards under the 2025 MIP to each NEO:

Long-Term Incentive Plan Awards

The LTIP is designed to: (1) to help promote leadership retention and management continuity as S&T continues to execute its longer-term strategic plan; (2) to reward management for strong sustained value creation and financial performance; and (3) to align our executives’ interests with those of our shareholders via appropriately-sized grants of equity compensation. The 2025 LTIP continues prior years goals and puts a greater focus on performance and serves to create a balance between long-term and short-term performance imperatives, beyond that offered by the annual cash incentive under the MIP.

The changes implemented in 2022 were maintained in 2025 for the LTIP awards. The target opportunities as a percentage of base salary remained at 50% for the President and the CFO and 40% for all other non-CEO NEOs. The CEO has a target opportunity of 100% in accordance with his employment agreement.

The 2025 LTIP contains the same Shareholder Protection Feature for all awards and the Minimum Gateway Requirement for the performance-based restricted shares as described earlier for the 2025 MIP. The Compensation Committee believes that these features, coupled with the restricted stock and claw-back requirements, provide for substantial protection against excessive or unnecessary risk-taking by any plan participant.

2025 Long-Term Incentive Awards

Effective April 1, 2025, the Compensation Committee awarded the NEOs equity denominated long-term incentive awards of restricted stock units (“RSUs”) under the 2025 LTIP. Grants were made at a grant price equal to $37.3983 per share, which was the average of the high and low price of S&T Common Stock for the ten trading days ending on the grant date.

Each NEO’s target award consists of the following:

S&T Bancorp, Inc. | 2026 Proxy Statement | 43

Compensation Discussion and Analysis

Time-based units vest in equal amounts on each anniversary of their grant date over three years. Performance-based units (“PRSUs”) may be earned over a three-year period based on the Company’s Return on Average Equity (“ROAE”) and Total Shareholder Return (“TSR”) performance relative to the Performance Peer Group (defined in “Use of Competitive Data” on page 39), as described in more detail below.

The following awards were granted under the 2025 LTIP to the NEOs:

2025 LTIP Performance Metrics

The Compensation Committee determined to utilize the same two metrics used to determine the percentage of the PRSU target earned through vesting of the PRSU awards (also referred to as performance shares) as utilized in the 2024 LTIP. In addition, the Compensation Committee determined to keep payout levels on the peer-relative ROAE metric at 50% of target (Threshold Performance), 100% of target (Target Performance) and 150% of target (Maximum Performance) and the peer-relative TSR to a modifier to the ROAE payout metric: -30% (Threshold or below), 0% (Target) and +30% (Maximum). We consider the upside on the ROAE payout metric combined with the TSR modifier to offer a long-term incentive that better aligns the interests of NEOs with shareholders. Lastly, our 2025 time-based restricted awards are scheduled to vest pro rata annually over three years after the grant date. The Compensation Committee believes that ROAE measures and incentivizes S&T’s long-term profitability vis-à-vis our peers, while our relative TSR captures our shareholder return vis-à-vis our peers.

(A) Return on Average Equity (“ROAE”) for 2025 through 2027 relative to the Performance Peer Group

Participants can earn from 0% to 150% of their PRSU Target based on this metric as summarized below:

44 | S&T Bancorp, Inc. | 2026 Proxy Statement

Compensation Discussion and Analysis

(B) Cumulative Total Shareholder Return for 2025 through 2027 relative to Performance Peer Group

The preliminary Earned PRSU Payout calculated above is subject to adjustment by S&T’s cumulative TSR for the three-year Performance Period. Participant’s PRSU awards can be modified by up to 30% higher or lower if S&T’s cumulative TSR is higher or lower than the 50^th percentile of the Peer Group.

The Modifier will vary depending on actual performance, and the payout curve rises continuously from Threshold to Target and from Target to Maximum. Therefore, to determine awards between Threshold and Target and Target and Maximum, linear interpolation would be utilized.

Vesting of 2022 Long-Term Incentive Plan Awards

The performance-based shares granted on April 1, 2022 vested on April 1, 2025 at 172%. S&T met the required threshold for 3 Year ROAE at the 66^th percentile for a payout of 132%. The 3-Year TSR modifier was at the 81^st percentile which met the requirements to achieve a 30% enhancement to the ROAE result (132% X 1.30 = 172%). The Compensation Committee approved the vesting of the time-based awards based on S&T meeting the Shareholder Protection Feature.

S&T does not currently grant awards of stock options, stock appreciation rights or similar option-like instruments and does not time the disclosure of material non-public information on any equity award dates for the purpose of affecting the value of such award.

Certain Other Benefits

S&T provides certain other benefits to the NEOs that are appropriately limited in scope and value. The primary benefits for the NEOs are a broad-based defined contribution retirement plan and welfare benefit plan, a nonqualified deferred compensation plan, and a defined benefit program. The Thrift Plan for Employees of S&T Bank (the “Thrift Plan”) is a broad-based qualified defined contribution plan. All employees may participate in the Thrift Plan with elective salary deferrals, or 401(k) contributions. During 2025, S&T made matching contributions equal to 100% of the first 1% of the employees’ eligible compensation and 50% of the next 5% of the employees’ eligible compensation, up to a maximum of 3.5% of all employees’ eligible compensation. More information regarding the other retirement benefits can be found beginning on page 53. The S&T Bank Welfare Benefit Plan is generally provided to all officers and full-time employees and includes provisions for medical reimbursement, dental coverage, vision care coverage, long-term disability income, a flexible spending account, a health savings account, and life insurance.

Because S&T’s executives frequently drive vehicles on company business, S&T may provide either a company car or a car allowance to executives, including the NEOs. Executives are responsible for reporting the amount of personal use of company cars to S&T, so that the taxable income from such use can be reported in the executives’ compensation. Executives who do not have a company car may receive an annual car allowance of up to $6,000, depending upon the frequency that the executive drives. The car allowance is fully taxable compensation. In his employment agreement, our CEO Mr. McComish received up to a $25,000 annual car allowance, which the Compensation Committee ultimately approved to be as a company car.

Lastly, S&T pays for certain members of senior management to belong to one or more private clubs if the member of management has significant customer contact and involvement in the community. S&T considers a

S&T Bancorp, Inc. | 2026 Proxy Statement | 45

Compensation Discussion and Analysis

social or country club to be an appropriate venue to entertain customers and to participate in various community functions. Expenses of a personal nature or related to a spouse are not paid by S&T.

Double Trigger Change in Control Severance Protections

S&T enters into change in control agreements with selected officers in senior management, including all the NEOs to help ensure that S&T’s leadership team remains engaged and focused should the organization ever become the target of a change in control where their jobs or ongoing compensation could be at risk. The primary terms and compensation payments contemplated by the agreements also include robust non-competition and non-solicitation provisions, one or both of which must be agreed to by the executive to receive the benefits provided.

The Compensation Committee believes that the change in control agreements provide reasonable protection to the individual members on the senior management team and thereby align senior management’s interest with the interest of S&T’s shareholders.

OTHER COMPENSATION-RELATED PROVISIONS

Mitigation in Plan Design Risk

The Compensation Committee considers, in establishing and reviewing the executive compensation program, whether the program encourages any unnecessary or excessive risk taking and concludes:

In addition, at least annually, the Compensation Committee discusses, evaluates and reviews with S&T’s CRO the compensation arrangements to ensure that: (i) the compensation plans for senior management (senior vice presidents or higher) do not encourage the members of senior management to take unnecessary and excessive risks that threaten the value of S&T, (ii) the compensation plans for employees do not pose unnecessary risks to S&T, and (iii) the compensation plans for employees do not encourage the manipulation of reported earnings to enhance the compensation of any of S&T’s employees.

Employment Agreements

S&T entered into employment agreements with each of Messrs. McComish and Antolik for their roles as CEO and President, respectively, on July 12, 2021. S&T does not provide employment agreements for any of the other NEOs. For more detail regarding the employment agreements for Messrs. McComish and Antolik see further discussion in Additional Narrative Information – Compensation Agreements on page 50.

EFFECT OF TAXATION ON COMPENSATION PROGRAMS (TAX CONSIDERATIONS)

As in the past, the Compensation Committee expects to continue to take into consideration the tax deductibility of compensation but reserves the right to maintain flexibility with respect to S&T’s executive compensation programs, including the awarding of compensation that may not be deductible when it believes that such payments are appropriate and in the best interests of the shareholders.

Despite the limited availability of Code Section 162(m) performance-based compensation exceptions following the Tax Cuts and Jobs Act of 2017, our Compensation Committee does not anticipate a shift away from variable or performance-based compensation payable to our NEOs. Similarly, we do not expect to apply less rigor in the process by which we establish performance goals or evaluate performance against pre-established goals with respect to compensation paid to our NEOs.

46 | S&T Bancorp, Inc. | 2026 Proxy Statement

COMPENSATION AND BENEFITS COMMITTEE REPORT

We, the Compensation and Benefits Committee of the Board of Directors of S&T Bancorp, Inc. (“S&T”), have reviewed and discussed the Compensation Discussion and Analysis included in this Proxy Statement with S&T’s management, and, based on such review and discussion, have recommended to the Board of Directors that the Compensation Discussion and Analysis be included in this Proxy Statement.

S&T Bancorp, Inc. | 2026 Proxy Statement | 47

EXECUTIVE COMPENSATION

The following table provides information concerning remuneration of the NEOs during 2023-2025.

Summary Compensation Table

48 | S&T Bancorp, Inc. | 2026 Proxy Statement

Executive Compensation

All Other Compensation

Grants of Plan-Based Awards for Fiscal Year 2025