    <SEC-DOCUMENT>0000950170-25-034173-index.html : 20250306
    <SEC-HEADER>0000950170-25-034173.hdr.sgml : 20250306
    <ACCEPTANCE-DATETIME>20250306072916
    ACCESSION NUMBER:		0000950170-25-034173
    CONFORMED SUBMISSION TYPE:	DEFA14A
    PUBLIC DOCUMENT COUNT:		7
    FILED AS OF DATE:		20250306
    DATE AS OF CHANGE:		20250306

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			FIRST BUSINESS FINANCIAL SERVICES, INC.
    		CENTRAL INDEX KEY:			0001521951
    		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
    		ORGANIZATION NAME:           	02 Finance
    		IRS NUMBER:				391576570
    		STATE OF INCORPORATION:			WI
    		FISCAL YEAR END:			1231

    	FILING VALUES:
    		FORM TYPE:		DEFA14A
    		SEC ACT:		1934 Act
    		SEC FILE NUMBER:	001-34095
    		FILM NUMBER:		25713616

    	BUSINESS ADDRESS:
    		STREET 1:		401 CHARMANY DRIVE
    		CITY:			MADISON
    		STATE:			WI
    		ZIP:			53719
    		BUSINESS PHONE:		608-238-8008

    	MAIL ADDRESS:
    		STREET 1:		401 CHARMANY DRIVE
    		STREET 2:		PO BOX 44961
    		CITY:			MADISON
    		STATE:			WI
    		ZIP:			53744

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	First Business Financial Services, Inc.
    		DATE OF NAME CHANGE:	20110527
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>DEFA14A
    <SEQUENCE>1
    <FILENAME>fbiz-20250304.htm
    <DESCRIPTION>DEFA14A
    <TEXT>
    Document 1 - file: fbiz-20250304.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>2
    <FILENAME>img75777704_0.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 2 - file: img75777704_0.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>3
    <FILENAME>img75777704_1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 3 - file: img75777704_1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>4
    <FILENAME>img75777704_2.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 4 - file: img75777704_2.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>img75777704_3.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: img75777704_3.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>img75777704_4.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: img75777704_4.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>img75777704_5.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: img75777704_5.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>