Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in Registration Statement (Nos. 333-163818 and 333-51538) on Form S-8 of our report dated June 22, 2018, appearing in this Annual Report on Form 11-K of The Bank of Greene County Employees’ Savings & Profit Sharing Plan and Trust for the year ended December 31, 2017.

/s/Bonadio & Co., LLP

Bonadio & Co., LLP

Syracuse, New York

June 22, 2018