-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 OCbWjnRKwqvjzeU5kfI3CL/ErYSoqiyIaXOLdvnrkfqbapJGQVnmKKAVw+QGew5W
 uPMZRX+yE+ufWngzq9w6DA==

<SEC-DOCUMENT>0001221127-03-000014.txt : 20031230
<SEC-HEADER>0001221127-03-000014.hdr.sgml : 20031230
<ACCEPTANCE-DATETIME>20031230085555
ACCESSION NUMBER:		0001221127-03-000014
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031226
FILED AS OF DATE:		20031230

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LEPOFSKY ROBERT
		CENTRAL INDEX KEY:			0001182721

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30027
		FILM NUMBER:		031076549

	MAIL ADDRESS:	
		STREET 1:		NINE HAMPSHIRE STREET
		CITY:			MANSFIELD
		STATE:			MA
		ZIP:			02048-9171

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MOLDFLOW CORP
		CENTRAL INDEX KEY:			0001103234
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-PREPACKAGED SOFTWARE [7372]
		IRS NUMBER:				043406763
		FISCAL YEAR END:			0620

	BUSINESS ADDRESS:	
		STREET 1:		430 BOSTON POST ROAD
		CITY:			WAYLAND
		STATE:			MA
		ZIP:			01778
		BUSINESS PHONE:		508-358-5848

	MAIL ADDRESS:	
		STREET 1:		430 BOSTON POST ROAD
		CITY:			WAYLAND
		STATE:			MA
		ZIP:			01778
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-12-26</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001103234</issuerCik>
        <issuerName>MOLDFLOW CORP</issuerName>
        <issuerTradingSymbol>MFLO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001182721</rptOwnerCik>
            <rptOwnerName>LEPOFSKY ROBERT</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MOLDFLOW CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>430 BOSTON POST ROAD</rptOwnerStreet2>
            <rptOwnerCity>WAYLAND</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01778</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>

        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.06</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-12-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-12-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>

    </derivativeTable>

    <footnotes>
        <footnote id="F1">This option is exercisable as to 50% of the shares on the first anniversary of the date of grant and the remaining 50% of the shares on the second anniversary of the date of grant.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Robert J. Lepofsky</signatureName>
        <signatureDate>2003-12-30</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----