<SUBMISSION>
<ACCESSION-NUMBER>0001284383-04-000002
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20040318
<FILING-DATE>20040322
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>FRIED BERNARD
<CIK>0001284383
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>001-13831
<FILM-NUMBER>04683263
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>31 MEADOWHILL DR
<CITY>TIBURON
<STATE>CA
<ZIP>94920
<PHONE>4154356639
</BUSINESS-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>QUANTA SERVICES INC
<CIK>0001050915
<ASSIGNED-SIC>1731
<IRS-NUMBER>742851603
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>1360 POST OAK BLVD
<STREET2>SUITE 2100
<CITY>HOUSTON
<STATE>TX
<ZIP>77056
<PHONE>7133506000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1360 POST OAK BLVD SUITE 2100
<CITY>HOUSTON
<STATE>TX
<ZIP>77056
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>c0001284383d20040322f3f.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2004-03-18</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001284383</rptOwnerCik>
            <rptOwnerName>FRIED BERNARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1360 POST OAK BOULEVARD, SUITE 2100</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77056</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></derivativeTable>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>Pamela L. Kunkemoeller, Atty in Fact</signatureName>
        <signatureDate>2004-03-22</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
