<SEC-DOCUMENT>0000842517-19-000035.txt : 20190214
<SEC-HEADER>0000842517-19-000035.hdr.sgml : 20190214
<ACCEPTANCE-DATETIME>20190214175507
ACCESSION NUMBER:		0000842517-19-000035
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20181231
FILED AS OF DATE:		20190214
DATE AS OF CHANGE:		20190214

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Schwind Jerome E
		CENTRAL INDEX KEY:			0001596032

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-18415
		FILM NUMBER:		19608824

	MAIL ADDRESS:	
		STREET 1:		2132 COBBLESTONE CT.
		CITY:			MT. PLEASANT
		STATE:			MI
		ZIP:			48858

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ISABELLA BANK Corp
		CENTRAL INDEX KEY:			0000842517
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				382830092
		STATE OF INCORPORATION:			MI
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		401 NORTH MAIN STREET
		CITY:			MT PLEASANT
		STATE:			MI
		ZIP:			48858
		BUSINESS PHONE:		9897729471

	MAIL ADDRESS:	
		STREET 1:		401 NORTH MAIN STREET
		CITY:			MT PLEASANT
		STATE:			MI
		ZIP:			48858

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ISABELLA BANK CORP
		DATE OF NAME CHANGE:	20080602

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	IBT BANCORP INC /MI/
		DATE OF NAME CHANGE:	19920703
</SEC-HEADER>
<DOCUMENT>
<TYPE>5
<SEQUENCE>1
<FILENAME>wf-form5_155018489326974.xml
<DESCRIPTION>FORM 5
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2018-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>0</form3HoldingsReported>

    <form4TransactionsReported>1</form4TransactionsReported>

    <issuer>
        <issuerCik>0000842517</issuerCik>
        <issuerName>ISABELLA BANK Corp</issuerName>
        <issuerTradingSymbol>ISBA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001596032</rptOwnerCik>
            <rptOwnerName>Schwind Jerome E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1280 QUEENSWAY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LAKE ISABELLA</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>48893</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>common</value>
            </securityTitle>
            <transactionDate>
                <value>2018-08-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value>L</value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>404.5705</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>29.50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5729.4009</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Shares previously held through the ESOP which were distributed and sold on August 29, 2018.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Debra A. Campbell, By Power of Attorney</signatureName>
        <signatureDate>2019-02-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
