S&T BANCORP INC

UNITED STATES

SECURITIES AND EXCHANGE

COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.

)

Filed by the Registrant

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Filed by a Party other than the Registrant

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Check the appropriate box:

(Name of registrant as specified in its charter)

(Name of person(s) filing proxy statement, if other than the registrant)

Payment of Filing Fee (Check all boxes that apply):

To my fellow shareholders: In 1902, a small Pennsylvania Bank began with a promise to make people its purpose. Over 120 years later, we’re still cultivating relationships firmly rooted in trust as we work together to build Our Shared Future. This strategic framework defines our purpose, values and drivers for profitable growth and creates a roadmap that guides our proactive steps to deliver long-term, sustainable financial performance. Our results in 2024 were driven through meaningful progress on our key business drivers, including consistent growth in our customer deposit franchise and ongoing improvement in asset quality. This diligent, focused approach has enabled us to grow from a single branch in Indiana, Pennsylvania, to an award-winning franchise that spans from central Ohio to Eastern Pennsylvania with over 70 locations.

People-Forward Banking

Our people are our differentiating characteristic and enduring strength. They live our purpose in a uniquely S&T way and foster a welcoming environment where all team members can work together to better the lives of our employees, customers, and communities.

At S&T, five values guide our attitudes and actions:

As a people-forward Bank, our success is directly tied to the engagement level of our employees. Our industry leading employee engagement was evidenced by S&T being honored as one of Forbes* America’s Best Midsized Employers in 2024 for the second consecutive year. We were also named an American Banker 2024 Best Banks to Work Forwinner, demonstrating how we make people our purpose and showing that our employees feel prioritized, valued, and supported as a critical part of our success. Additionally, because of our industry-leading employee engagement scores, S&T was recognized by Energage as a Financial Services Industry Top Workplaces 2024 winner.

Engaging With Our Communities

At S&T, giving back to the community is at the center of our people-forward purpose and our commitment is evidenced in our donations of time and resources in 2024.

For the third year, our employees were offered up to 16 hours of paid, annual volunteer hours to support their local communities. I am proud to share that our employees completed over 25,000 community service hours and provided more than 700 hours of financial education, volunteering at over 1,000 organizations across our footprint.

Beyond our volunteerism in 2024, S&T made financial contributions in support of organizations that make a positive impact on our customers and communities. Over $180,000 was donated to United Way from our employee-sponsored annual campaign. For the second year, S&T partnered with Alex’s Lemonade Stand

Foundation (ALSF), hosting lemonade stands at every S&T location and raising over $100,000 in support of childhood cancer research through the generosity of our employees, customers, and members of our local communities. Beyond the donation efforts to these organizations and a myriad of others, an additional $400,000 was donated by S&T to qualifying charities in 2024.

Additionally, S&T provided over $15 million in community development loans throughout 2024 in support of affordable housing, economic development needs and to revitalize or stabilize underserved areas.

Financial Highlights

Our engaged employees, working together for our customers and focused on our business drivers, delivered strong 2024 full year results including consistent growth in our customer deposit franchise and ongoing improvement in asset quality.

Financial highlights for 2024 include**:

As a result of our financial performance, S&T was named as one of Forbes* 2024 America’s Best Banks: This annual ranking is based on metrics that measure growth, credit quality, profitability, and stock performance. Moreover, S&T was named on Bank Director’s 2024 RankingBanking list. This annual study ranks institutions on profitability, capital, and asset quality metrics to gauge the performance of public commercial and savings banks. S&T was also pleased to be included in the Piper Sandler Sm-All Stars Class of 2024, a list that identifies the top performing small-cap banks and thrifts across the country related to growth, profitability, credit quality, and capital strength.

The Past Shapes the Future

A lot has changed since our Bank got its start more than 122 years ago. But one thing hasn’t: our dedication to earning and keeping the trust of the many customers and communities we serve across our footprint.

Looking ahead, we are dedicated to continued growth and forward progress on our strategic objectives, seeking opportunities to have an even greater impact on Our Shared Future.

On behalf of everyone at S&T Bank, I’d like to thank you for placing your trust in us. We work to earn it every day.

Kindly,

Chris McComish CEO

DATE AND TIME May 13, 2025, 10:00 a.m. Eastern Time via virtual online meeting only (www.virtualshareholdermeeting.com/STBA2025)

HOW TO VOTE

By Telephone Call (1-800-690-6903)

By Internet Visit www.proxyvote.com

By Mail Sign, date and return proxy card

To the Shareholders of

S&T Bancorp, Inc.:

Notice is hereby given that the Annual Meeting of Shareholders of S&T Bancorp, Inc. (“S&T”) will be held on May 13, 2025, at 10:00 a.m. Eastern Time, via virtual online meeting only (www.virtualshareholdermeeting.com/STBA2025) for considering and voting on the following matters:

Only shareholders of record at the close of business on February 28, 2025 are entitled to notice of and to vote at such meeting or any adjournment thereof.

To participate in the virtual Annual Meeting atwww.virtualshareholdermeeting.com/STBA2025, you need to use the 16-digit control number included on your Notice of Internet Availability of Proxy Materials (“Notice”), on your proxy card or on the instructions that accompanied your proxy materials. We encourage you to allow ample time for online check-in, which will begin at 9:30 a.m. Eastern Time. Please note that there is noin-person annual meeting for you to attend.

By Order of the Board of Directors,

Rachel L. Smydo

Secretary

Indiana, Pennsylvania

March 31, 2025

IMPORTANT

YOUR VOTE IS IMPORTANT, AND WE APPRECIATE YOUR TAKING THE TIME TO VOTE PROMPTLY USING ONE OF THE VOTING METHODS DESCRIBED IN THE PROXY STATEMENT.

THE BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT THE SHAREHOLDERS VOTE FOR THE ELECTION AS DIRECTORS OF ALL OF THE NOMINEES NAMED IN THIS PROXY STATEMENT, FOR THE RATIFICATION OF THE SELECTION OF ERNST & YOUNG LLP AS S&T’S INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR FISCAL YEAR 2025, AND FOR THE APPROVAL OF THE COMPENSATION OF S&T’S NAMED EXECUTIVE OFFICERS.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF

PROXY MATERIALS FOR THE 2025 ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD ON MAY 13, 2025: OUR PROXY STATEMENT, 2024 ANNUAL REPORT AND NOTICE OF

ANNUAL MEETING OF SHAREHOLDERS ARE AVAILABLE ATWWW.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 in place of the complete proxy package. For our 2025 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 31, 2025, to inform them of the electronic availability of the proxy materials 40 days in advance of the Annual Meeting.