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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 L8On228UsAQJdjUbPXjvBQVSimZMF50w2TTuF36v9wbRua467THtP0xGpupOFUI/
 zZyoVLV1jSUzMV58Say8DA==

<SEC-DOCUMENT>0001254037-04-000007.txt : 20041229
<SEC-HEADER>0001254037-04-000007.hdr.sgml : 20041229
<ACCEPTANCE-DATETIME>20041229170434
ACCESSION NUMBER:		0001254037-04-000007
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041227
FILED AS OF DATE:		20041229
DATE AS OF CHANGE:		20041229

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SOLOWAY RICHARD
		CENTRAL INDEX KEY:			0001254037

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10004
		FILM NUMBER:		041231723

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		6318429400X120

	MAIL ADDRESS:	
		STREET 1:		333 BAYVIEW AVENUE
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NAPCO SECURITY SYSTEMS INC
		CENTRAL INDEX KEY:			0000069633
		STANDARD INDUSTRIAL CLASSIFICATION:	COMMUNICATIONS EQUIPMENT, NEC [3669]
		IRS NUMBER:				112277818
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		333 BAYVIEW AVE
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701
		BUSINESS PHONE:		5168429400

	MAIL ADDRESS:	
		STREET 1:		333 BAYVIEW AVE
		STREET 2:		XXXXXXXXXXXXXXXXXXX
		CITY:			AMITYVILLE
		STATE:			NY
		ZIP:			11701
</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>2004-12-27</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000069633</issuerCik>
        <issuerName>NAPCO SECURITY SYSTEMS INC</issuerName>
        <issuerTradingSymbol>NSSC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001254037</rptOwnerCik>
            <rptOwnerName>SOLOWAY RICHARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>333 BAYVIEW AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>AMITYVILLE</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>11701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and Secretary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>NAPCO Security Systems, Inc.</value>
            </securityTitle>
            <transactionDate>
                <value>2004-12-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>11327</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2576055</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>NAPCO Security Systems, Inc.</value>
            </securityTitle>
            <transactionDate>
                <value>2004-12-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>74650</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.041</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2501405</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>NAPCO Security Systems, Inc.</value>
            </securityTitle>
            <transactionDate>
                <value>2004-12-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20223</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.655</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2481182</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Completion of June 1, 2004 planned sale, including 20% stock dividend.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Richard Soloway</signatureName>
        <signatureDate>2004-12-29</signatureDate>
    </ownerSignature>
</ownershipDocument>

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