-----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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 B2OP+DOpTx+bG4HWnTbVCw==

<SEC-DOCUMENT>0001179110-09-014092.txt : 20091002
<SEC-HEADER>0001179110-09-014092.hdr.sgml : 20091002
<ACCEPTANCE-DATETIME>20091002172419
ACCESSION NUMBER:		0001179110-09-014092
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091001
FILED AS OF DATE:		20091002
DATE AS OF CHANGE:		20091002

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Francis John J
		CENTRAL INDEX KEY:			0001377475

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51468
		FILM NUMBER:		091103529

	MAIL ADDRESS:	
		STREET 1:		651 S STRATFORD DRIVE SUITE 100
		CITY:			MERIDIAN
		STATE:			ID
		ZIP:			83642

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MWI Veterinary Supply, Inc.
		CENTRAL INDEX KEY:			0001323974
		STANDARD INDUSTRIAL CLASSIFICATION:	WHOLESALE-MEDICAL, DENTAL & HOSPITAL EQUIPMENT & SUPPLIES [5047]
		IRS NUMBER:				020620757
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		651 S. STRATFORD DRIVE
		STREET 2:		SUITE 100
		CITY:			MERIDIAN
		STATE:			ID
		ZIP:			83642
		BUSINESS PHONE:		(800) 824-3703

	MAIL ADDRESS:	
		STREET 1:		651 S. STRATFORD DRIVE
		STREET 2:		SUITE 100
		CITY:			MERIDIAN
		STATE:			ID
		ZIP:			83642

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MWI Holdings, Inc.
		DATE OF NAME CHANGE:	20050415
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001323974</issuerCik>
        <issuerName>MWI Veterinary Supply, Inc.</issuerName>
        <issuerTradingSymbol>MWIV</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001377475</rptOwnerCik>
            <rptOwnerName>Francis John J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>651 S. STRATFORD DRIVE, SUITE 100</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MERIDIAN</rptOwnerCity>
            <rptOwnerState>ID</rptOwnerState>
            <rptOwnerZipCode>83642</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP and General Manager</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2009-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>68</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>38.50</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6005</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2009-10-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>342</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>38.27</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5663</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Surrender of shares to satisfy tax withholding obligation incident to vesting of restricted stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Ryan Cleverley as attorney-in-fact for John J. Francis</signatureName>
        <signatureDate>2009-10-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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