-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 EF8Qzsgpqd1fvEATxmZnGA==

<SEC-DOCUMENT>0000926044-10-000130.txt : 20100301
<SEC-HEADER>0000926044-10-000130.hdr.sgml : 20100301
<ACCEPTANCE-DATETIME>20100301152157
ACCESSION NUMBER:		0000926044-10-000130
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20100225
FILED AS OF DATE:		20100301
DATE AS OF CHANGE:		20100301

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WILLIAMS PAUL C
		CENTRAL INDEX KEY:			0001425329

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14209
		FILM NUMBER:		10644089

	MAIL ADDRESS:	
		STREET 1:		311 WOODWORTH AVENUE
		CITY:			ALMA
		STATE:			MI
		ZIP:			48881

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FIRSTBANK CORP
		CENTRAL INDEX KEY:			0000778972
		STANDARD INDUSTRIAL CLASSIFICATION:	STATE COMMERCIAL BANKS [6022]
		IRS NUMBER:				382633910
		STATE OF INCORPORATION:			MI
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		311 WOODWORTH AVE
		STREET 2:		PO BOX 1029
		CITY:			ALMA
		STATE:			MI
		ZIP:			48801
		BUSINESS PHONE:		5174633131

	MAIL ADDRESS:	
		STREET 1:		311 WOODWORTH AVE
		CITY:			ALMA
		STATE:			MI
		ZIP:			48801
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>williams4_022510.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-02-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000778972</issuerCik>
        <issuerName>FIRSTBANK CORP</issuerName>
        <issuerTradingSymbol>FBMI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001425329</rptOwnerCik>
            <rptOwnerName>WILLIAMS PAUL C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>311 WOODWORTH AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ALMA</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>48881</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Controller</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-02-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1550</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>6.0964</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1003.8606</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Total includes all shares acquired under the Company's dividend reinvestment plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David Miller, as Attorney in Fact for Paul Williams</signatureName>
        <signatureDate>2010-03-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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