Exhibit 15

Report of Independent Registered Public Accounting Firm

May 6, 2022

Arrow Financial Corporation

Glens Falls, New York

Re: Registration Statement Form S-3 (No. 333-243662, 333-258552 and 333-263812) and Form S-8 (No. 333-151550, No. 333-188479, No. 333-188480, and No. 333-238096)

With respect to the subject registration statement, we acknowledge our awareness of the use therein of our report dated May 6, 2022 related to our review of interim financial information.

Pursuant to Rule 436 under the Securities Act of 1933 (the Act), such report is not considered part of a registration statement prepared or certified by an independent registered public accounting firm, or a report prepared or certified by an independent registered public accounting firm within the meaning of Sections 7 and 11 of the Act.

/s/ KPMG LLP

Albany, New York