<SEC-DOCUMENT>0001144215-13-000044.txt : 20130501
<SEC-HEADER>0001144215-13-000044.hdr.sgml : 20130501
<ACCEPTANCE-DATETIME>20130501162106
ACCESSION NUMBER:		0001144215-13-000044
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20130501
FILED AS OF DATE:		20130501
DATE AS OF CHANGE:		20130501

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BROWNING PETER C
		CENTRAL INDEX KEY:			0001176402

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-16583
		FILM NUMBER:		13803469

	MAIL ADDRESS:	
		STREET 1:		C/O ENPRO INDUSTRIES INC
		STREET 2:		5605 CARNEGIE BLVD
		CITY:			CHARLOTTE
		STATE:			NC
		ZIP:			28209-4674

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ACUITY BRANDS INC
		CENTRAL INDEX KEY:			0001144215
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRIC LIGHTING & WIRING EQUIPMENT [3640]
		IRS NUMBER:				582632672
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0831

	BUSINESS ADDRESS:	
		STREET 1:		1170 PEACHTREE STREET, NE
		STREET 2:		SUITE 2300
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30309-7676
		BUSINESS PHONE:		404-853-1400

	MAIL ADDRESS:	
		STREET 1:		1170 PEACHTREE STREET, NE
		STREET 2:		SUITE 2300
		CITY:			ATLANTA
		STATE:			GA
		ZIP:			30309-7676

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	L&C SPINCO INC
		DATE OF NAME CHANGE:	20010629
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_136743965583220.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-05-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001144215</issuerCik>
        <issuerName>ACUITY BRANDS INC</issuerName>
        <issuerTradingSymbol>AYI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001176402</rptOwnerCik>
            <rptOwnerName>BROWNING PETER C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ACUITY BRANDS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1170 PEACHTREE STREET, NESUITE 2400</rptOwnerStreet2>
            <rptOwnerCity>ATLANTA</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>30309</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Units</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2013-05-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>344</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>72.71</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>344.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21248</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Stock Units are accrued under the Issuer's Nonemployee Directors' Deferred Compensation Plan (formerly known as the Nonemployee Directors' Stock Unit Plan) and are payable in shares upon retirement in either lump sum or five annual installments.  Accruals include required and elective deferral of director fees.   During the Reporting Period, fees paid to the Reporting Person resulted in an increase in the number of units held.</footnote>
        <footnote id="F2">1-for-1</footnote>
        <footnote id="F3">Stock Units issued pursuant to the Plan are payable in common shares upon retirement in either a lump sum or five annual installments.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peter C. Browning</signatureName>
        <signatureDate>2013-05-01</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
