    <SEC-DOCUMENT>0000950170-25-053505-index.html : 20250414
    <SEC-HEADER>0000950170-25-053505.hdr.sgml : 20250414
    <ACCEPTANCE-DATETIME>20250414080106
    ACCESSION NUMBER:		0000950170-25-053505
    CONFORMED SUBMISSION TYPE:	DEFA14A
    PUBLIC DOCUMENT COUNT:		4
    FILED AS OF DATE:		20250414
    DATE AS OF CHANGE:		20250414

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			FINANCIAL INSTITUTIONS INC
    		CENTRAL INDEX KEY:			0000862831
    		STANDARD INDUSTRIAL CLASSIFICATION:	NATIONAL COMMERCIAL BANKS [6021]
    		ORGANIZATION NAME:           	02 Finance
    		EIN:				160816610
    		STATE OF INCORPORATION:			NY
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEFA14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	000-26481
    		FILM NUMBER:		25834243

    	BUSINESS ADDRESS:
    		STREET 1:		220 LIBERTY STREET
    		CITY:			WARSAW
    		STATE:			NY
    		ZIP:			14569
    		BUSINESS PHONE:		5857861100

    	MAIL ADDRESS:
    		STREET 1:		220 LIBERTY STREET
    		CITY:			WARSAW
    		STATE:			NY
    		ZIP:			14569
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEFA14A
    <SEQUENCE>1
    <FILENAME>fisi_2025_notice_and_acc.htm
    <DESCRIPTION>DEFA14A
    <TEXT>
    Document 1 - file: fisi_2025_notice_and_acc.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>img255940554_0.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: img255940554_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>img255940554_1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: img255940554_1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>img255940554_2.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: img255940554_2.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>