<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2010-08-16</periodOfReport>

    <dateOfOriginalSubmission>2010-08-17</dateOfOriginalSubmission>

    <issuer>
        <issuerCik>0001105472</issuerCik>
        <issuerName>SONUS NETWORKS INC</issuerName>
        <issuerTradingSymbol>SONS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000903662</rptOwnerCik>
            <rptOwnerName>SEVERINO PAUL J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SONUS NETWORKS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>4 TECHNOLOGY PARK DRIVE</rptOwnerStreet2>
            <rptOwnerCity>WESTFORD</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01886</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2010-08-16</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>509572</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares of restricted stock vest immediately prior to the Issuer's 2011 Annual Meeting of Stockholders.</footnote>
    </footnotes>

    <remarks>This amendment on Form 4/A to the Form 4 filed on August 17, 2010 (the &quot;Original Form 4&quot;) is made solely to correct footnote 1 in its entirety.  Except for the foregoing, no new or revised transactions or holdings are being reported.  All other information in the Original Form 4 remains the same.</remarks>

    <ownerSignature>
        <signatureName>Paul J. Severino</signatureName>
        <signatureDate>2011-06-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
