FINANCIAL INSTITUTIONS INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule

14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

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FINANCIAL INSTITUTIONS, INC.

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FROM OUR INDEPENDENT BOARD CHAIR

FELLOW SHAREHOLDERS: On behalf of the Board of Directors of Financial Institutions, Inc., thank you for your interest and investment in our Company. Our Board and executive management team remain committed to leveraging our proven operating model and strategic framework to grow our diverse franchise, strengthen our business and deliver on our responsibility to drive long-term value for you, our shareholders. During my tenure as a director of this Company, we have persevered through several challenging operating environments. I remain very confident in our ability to weather the current economic cycle by continuing to focus on delivering meaningful customer experiences, prioritizing safety and soundness, and engaging in sustainable business practices. Our directors bring diverse expertise to the Board. They represent an array of different industries and backgrounds that are highly valuable to the Board. Over 45% of our independent directors reflect gender or ethnic diversity, and four of the Board’s six committees are led by women or an ethnically diverse director.

Our Executive Management Committee (“EMC”) is similarly experienced and diverse. With an average of 20 years of experience in the financial services industry, including President and CEO Marty Birmingham’s expansive 35-year career in banking, our executives bring deep financial industry expertise to their roles. Our executive team is focused on driving greater operational efficiency, enhancing our brand strategy, ensuring risk management excellence, and maintaining our disciplined and consistent focus on talent development. Two of the seven EMC members reporting to our CEO are women and we continue to prioritize fostering a diverse and inclusive culture across the entire Company.

Engagement with shareholders continues to be very important to us. We proactively engage with our shareholders through conferences, virtual andin-person meetings, and publicly available quarterly investor calls. We invite you to read our 2024 Proxy Statement and encourage you to vote online to ensure that you are represented at our annual meeting.

The coming year will, undoubtably, bring new challenges. But we believe that our continued focus on delivering exceptional customer experiences, while embracing technology and innovation, will drive our future success and deliver long-term value to our shareholders.

Thank you once again for your support of our Company.

Sincerely,

Susan R. Holliday

Chair of the Board

FROM OUR CEO

FELLOW SHAREHOLDERS:

In 2023, amid the incredible pressures put on the banking industry, your Company was successful in defending deposits, growing relationships with new and existing customers, strengthening liquidity and capital and positioning itself for the future. We broadened Five Star Bank’s geographic reach through a new commercial loan office in Syracuse, NY serving the Central New York region. We merged our wealth management subsidiaries, thereby enhancing the size and scale of Courier Capital, LLC into one of the largest registered investment advisory firms in Western New York. In addition, we realigned key areas of our organization and made changes to our executive leadership team that strengthen our ability to execute our long-term strategy. Throughout this, we remained active and engaged in the communities we serve. Our 2023 Community Report highlights many of the ways we support our communities, including through grants, financial literacy education and volunteerism, while our 2024 Corporate Sustainability Report provides detail on our sustainable business practices.

We cordially invite you to our 2024 Annual Meeting of Shareholders on Wednesday, June 5, 2024, at 10:00 am, Eastern Time. The meeting will be held in virtual format through a live webcast, accessible at www.virtualshareholdermeeting.com/FISI2024.

You will be asked to vote on several items including the election of directors, compensation of our named executive officers (thesay-on-pay vote), the frequency of such compensation votes, and the ratification of the appointment of RSM US LLP to serve as our independent registered public accounting firm for 2024. Your vote is important, and we encourage you to read the proxy statement and vote your shares as promptly as possible. Proxy materials are again being provided in a virtual format this year, expediting delivery to shareholders, lowering expenses and reducing the environmental impact of our meeting.

Information on how to attend the annual meeting, vote and submit questions is provided in the attached notice of annual meeting.

On behalf of the Company’s executive and senior leadership team, I thank you for your continued support of and investment in Financial Institutions, Inc.

Cordially,

Martin K. Birmingham

President and Chief Executive Officer

TABLE OF CONTENTS

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This Proxy Statement contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements provide current expectations or forecasts of future results or events and include, among others:

These forward-looking statements are based on management’s current expectations and beliefs and are not guarantees of future results, nor should they be relied upon as representing management’s views as of any subsequent date. Forward-looking statements involve significant risks and uncertainties and actual results may differ materially from those presented, either expressed or implied, in this Proxy Statement. For a discussion of some of the risks and important factors that could cause actual results to differ from such forward-looking statements, please see the risks and other factors detailed from time to time in the Company’s most recent periodic reports on Form 10-K and Form 10-Q and other filings with the Securities and Exchange Commission (“SEC”).

We caution readers not to place undue reliance on any forward-looking statements, which speak only as of the date made. Except as required by law, we do not undertake, and specifically disclaim any obligation to publicly release any revisions to any forward-looking statements to reflect the occurrence of anticipated or unanticipated events or circumstances after the date of such statements.

NOTICE OF THE ANNUAL MEETING OF SHAREHOLDERS