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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-08-18</periodOfReport>

    <issuer>
        <issuerCik>0001170534</issuerCik>
        <issuerName>MITEL NETWORKS CORP</issuerName>
        <issuerTradingSymbol>MITL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001692681</rptOwnerCik>
            <rptOwnerName>Bevington Graham</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>350 LEGGET DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2>OTTAWA, A6</rptOwnerStreet2>
            <rptOwnerCity>K2K</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>2W7</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>See Remarks</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Options (Common Shares)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-08-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>30000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-07-15</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents 30,000 unexercised and out-of-the-money stock options previously granted to Mr. Bevington that expired on August 18, 2017. The expiry date for such options had been extended in accordance with the 2006 Equity Incentive Plan, to August 18, 2017 as a result of the original expiry date of July 15, 2017 coinciding with a black-out period for the Issuer.</footnote>
        <footnote id="F2">30,000 stock options to purchase Common Shares of the Company were granted to Mr. Bevington on July 15, 2010. 1,875 options vested on October 15, 2010 and vested in equal installments every three months thereafter until July 15, 2014.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Graham Bevington</signatureName>
        <signatureDate>2017-08-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
