-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 CwScTVterEXJ4Vo3TEjexp9y1BWV7idDlZZJ2RIxp8gPEXia7f0NeQdrPm4Otoad
 /24pY3kgGmf7IUhIfJLWSw==

<SEC-DOCUMENT>0000790715-06-000009.txt : 20060117
<SEC-HEADER>0000790715-06-000009.hdr.sgml : 20060116
<ACCEPTANCE-DATETIME>20060117194209
ACCESSION NUMBER:		0000790715-06-000009
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051028
FILED AS OF DATE:		20060117
DATE AS OF CHANGE:		20060117

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			LOWE KENNETH A
		CENTRAL INDEX KEY:			0001245501

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-32207
		FILM NUMBER:		06534196

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		4082624003

	MAIL ADDRESS:	
		STREET 1:		1221 CALIFORNIA CIRCLE
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SIGMA DESIGNS INC
		CENTRAL INDEX KEY:			0000790715
		STANDARD INDUSTRIAL CLASSIFICATION:	COMPUTER PERIPHERAL EQUIPMENT, NEC [3577]
		IRS NUMBER:				942848099
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			0131

	BUSINESS ADDRESS:	
		STREET 1:		1221 CALIFORNIA CIRCLE
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035
		BUSINESS PHONE:		4082629003

	MAIL ADDRESS:	
		STREET 1:		1221 CALIFORNIA CIRCLE
		CITY:			MILPITAS
		STATE:			CA
		ZIP:			95035
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-10-28</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000790715</issuerCik>
        <issuerName>SIGMA DESIGNS INC</issuerName>
        <issuerTradingSymbol>sigm</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001245501</rptOwnerCik>
            <rptOwnerName>LOWE KENNETH A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1221 CALIFORNIA CIRCLE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILPITAS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95035</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>V.P. of Marketing</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>9.89</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-10-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>9.89</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2006-10-28</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-10-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>189000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Granted to the reporting person under the Company's 2001 Employee Stock Option Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/Ken Lowe</signatureName>
        <signatureDate>2006-01-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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