<SEC-DOCUMENT>0000892712-21-000290.txt : 20210818
<SEC-HEADER>0000892712-21-000290.hdr.sgml : 20210818
<ACCEPTANCE-DATETIME>20210818163406
ACCESSION NUMBER:		0000892712-21-000290
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210816
FILED AS OF DATE:		20210818
DATE AS OF CHANGE:		20210818

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Seiler David R.
		CENTRAL INDEX KEY:			0001672596

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34095
		FILM NUMBER:		211187051

	MAIL ADDRESS:	
		STREET 1:		401 CHARMANY DRIVE
		CITY:			MADISON
		STATE:			WI
		ZIP:			53719

ISSUER:		

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

	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>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-08-16</periodOfReport>

    <issuer>
        <issuerCik>0001521951</issuerCik>
        <issuerName>FIRST BUSINESS FINANCIAL SERVICES, INC.</issuerName>
        <issuerTradingSymbol>FBIZ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001672596</rptOwnerCik>
            <rptOwnerName>Seiler David R.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>401 CHARMANY DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MADISON</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53719</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Operating Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-08-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>338</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.65</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15688</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">4,000 shares are held by the David &amp; Lisa Seiler Revocable Trust.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peter J. Wilder (pursuant to Power of Attorney filed previously)</signatureName>
        <signatureDate>2021-08-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
