ARROW FINANCIAL CORP

proxy statement of Adirondack, which also constitutes a prospectus of Arrow, that has been sent to shareholders of Adirondack seeking certain approvals related to the proposed transaction. Arrow may file with the SEC other relevant documents concerning the proposed transaction. This communication does not constitute an offer to sell or a solicitation of an offer to buy any securities or a solicitation of any vote or approval, nor shall there be any offer or sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offer of securities shall be made except by means of a prospectus meeting the requirements of the Securities Act of 1933, as amended. INVESTORS AND SHAREHOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT ON FORM S-4, THE PROXY STATEMENT/PROSPECTUS INCLUDED WITHIN THE REGISTRATION STATEMENT ON FORM S-4 AND ANY OTHER RELEVANT DOCUMENTS FILED OR TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED TRANSACTION, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT ARROW, ADIRONDACK, AND THE PROPOSED TRANSACTION. Investors and shareholders will be able to obtain a free copy of the registration statement, including the proxy statement/prospectus, as well as other relevant documents filed with the SEC containing information about Arrow, without charge, at the SEC’s website www.sec.gov. Copies of documents filed with the SEC by Arrow will be made available free of charge in the “Documents” section of Arrow’s website, www.arrowfinancial.com, under the heading “Filings.” The information on Arrow’s website is not, and shall not be deemed to be, a part of this communication or incorporated into other filings Arrow makes with the SEC. Participants in Solicitation Adirondack, Arrow, and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from shareholders of Adirondack in respect of the proposed transaction under the rules of the SEC. Information regarding Arrow’s directors and executive officers is available in its definitive proxy statement, which was filed with the SEC on April 23, 2026 and certain other documents filed by Arrow with the SEC. Other information regarding the participants in the solicitation of proxies in respect of the proposed transaction and a description of their direct and indirect interests, by security holdings or otherwise, is contained in the proxy statement/prospectus and other relevant materials filed or to be filed with the SEC.

Acknowledgements Annual Meeting Technical Support Justin Murberg, CPA Audit Senior Manager Frank Arren Inspector of Elections Benjamin M. Azoff Attorneys

Arrow Overview

Our Family of Companies

Our Market as of April 30, 2026 Insurance Offices Bank Branches 938 • $4.5 billion in assets • 575 plus employees • Primary service area population of more than 1.1 million

Our Philanthropy

Welcome, Mr. Jahnel Darrin M. Jahnel CEO and Co-Founder, Jahnel Group Effective November 25, 2025

Thank You, Ms. Miller Elizabeth A. Miller President and CEO, Miller Mechanical Services, Inc.

Our Directors David S. DeMarco President and CEO, Arrow Financial Corporation Colin L. Read, PhD Professor – Department of Economics and Finance, SUNY Plattsburgh James M. Dawsey President, MLB Construction Services, LLC Raymond F. O’Conor Retired President and CEO, Saratoga National Bank Dr. Kristine D. Duffy Strategic Advisor, Behan Communications Daniel J. White Retired Managing Partner, KPMG LLP Albany Mark L. Behan Founder and President, Behan Communications, Inc. David G. Kruczlnicki Retired President and CEO, Glens Falls Hospital Tenée R. Casaccio, AIA Chair Managing Principal, JMZ Architects and Planners, P.C. Darrin M. Jahnel CEO and Co-Founder, Jahnel Group Gregory J. Champion Retired Chief Legal Officer, Syncromune, Inc. Philip Morris CEO, Proctors Collaborative

Our Executive Management Michael Jacobs EVP and Chief Information Officer Penko K. Ivanov SEVP, Chief Financial Officer, Treasurer and Chief Accounting Officer David S. DeMarco President and CEO Brooke M. Pancoe EVP and Chief Human Resources Officer Marc J. Yrsha SEVP and Chief Banking Officer Andrew J. Wise SEVP and Chief Risk Officer

Our Senior Management Douglas Thorn SVP and Director of Insurance Operations Leslie Munger SVP and Director of Compliance and Risk Ginny Sullivan SVP and Director of Residential Lending Kurt Moser SVP and Director of Corporate Banking Wendy Lanzone SVP and CEX Director of Deposit and Loan Services Dave Riihimaki SVP and Director of Credit Administration Annette Reitano SVP and Director of Marketing and Communications Ian Williams SVP and Director of Retail and Business Banking Arleen Girard SVP and Director of Business Services Scott Duggleby SVP and Director of Wealth Management Ryan Case SVP and Capital Region Market Executive Wendy Brust SVP and Director of Information Technology Candice Healy SVP and Director of Retail Banking Harry Kabalian SVP and Director of Financial Planning & Analysis and Treasury Alex Rusate SVP and Director of Internal Audit Amy Merchant SVP and Director of Employee Total Rewards

Business Meeting

2026 Shareholder Voting Proposals 1. The election of four Class A Directors to three (3) year terms, each to serve until their successor has been duly elected and qualified. 2. Advisory