-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 B2wzggSiosaHF3kacLO/mTcOXYo1CbDAGaQ3BVsznS1PGr4cZeZBGneRvM4ciQhE
 LU4PQgqYjjVZUvKFeIKxOg==

<SEC-DOCUMENT>0001321312-05-000001.txt : 20050329
<SEC-HEADER>0001321312-05-000001.hdr.sgml : 20050329
<ACCEPTANCE-DATETIME>20050329171829
ACCESSION NUMBER:		0001321312-05-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050324
FILED AS OF DATE:		20050329
DATE AS OF CHANGE:		20050329

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Keel Frank
		CENTRAL INDEX KEY:			0001321312

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-10004
		FILM NUMBER:		05710529

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		727-372-8659

	MAIL ADDRESS:	
		STREET 1:		4664 MILL RUN DRIVE
		CITY:			NEW PORT RICHEY
		STATE:			FL
		ZIP:			34653
</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>2005-03-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001321312</rptOwnerCik>
            <rptOwnerName>Keel Frank</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4664 MILL RUN DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW PORT RICHEY</rptOwnerCity>
            <rptOwnerState>FL</rptOwnerState>
            <rptOwnerZipCode>34653</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>NAPCO Security Systems, Inc.</value>
            </securityTitle>
            <transactionDate>
                <value>2005-03-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>600</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10.7</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <ownerSignature>
        <signatureName>Frank Keel</signatureName>
        <signatureDate>2005-03-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----