<SEC-DOCUMENT>0001134702-17-000004.txt : 20170228
<SEC-HEADER>0001134702-17-000004.hdr.sgml : 20170228
<ACCEPTANCE-DATETIME>20170228182825
ACCESSION NUMBER:		0001134702-17-000004
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20170224
FILED AS OF DATE:		20170228
DATE AS OF CHANGE:		20170228

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			QUANTA SERVICES INC
		CENTRAL INDEX KEY:			0001050915
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRICAL WORK [1731]
		IRS NUMBER:				742851603
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2800 POST OAK BLVD
		STREET 2:		SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175
		BUSINESS PHONE:		7133506000

	MAIL ADDRESS:	
		STREET 1:		2800 POST OAK BLVD SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JENSEN DERRICK A
		CENTRAL INDEX KEY:			0001134702

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13831
		FILM NUMBER:		17650108

	MAIL ADDRESS:	
		STREET 1:		QUANTA SERVICES, INC.
		STREET 2:		2800 POST OAK BLVD., SUITE 2600
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77056-6175
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_148832449123831.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-02-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001050915</issuerCik>
        <issuerName>QUANTA SERVICES INC</issuerName>
        <issuerTradingSymbol>PWR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001134702</rptOwnerCik>
            <rptOwnerName>JENSEN DERRICK A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2800 POST OAK BLVD., SUITE 2600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77056-6175</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-02-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>16305</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>37.659</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>194802</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $37.65 to $37.695, inclusive. The reporting person undertakes to provide to Quanta Services, Inc., any security holder of Quanta Services, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Carolyn M. Campbell, Atty-in-Fact</signatureName>
        <signatureDate>2017-02-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
