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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-02-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000916230</issuerCik>
        <issuerName>PROTECTION ONE INC</issuerName>
        <issuerTradingSymbol>PONN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001281075</rptOwnerCik>
            <rptOwnerName>POI ACQUISITION LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001122322</rptOwnerCik>
            <rptOwnerName>QUADRANGLE CAPITAL PARTNERS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FL</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001281078</rptOwnerCik>
            <rptOwnerName>QUADRANGLE CAPITAL PARTNERS A LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001122313</rptOwnerCik>
            <rptOwnerName>QUADRANGLE SELECT PARTNERS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001271784</rptOwnerCik>
            <rptOwnerName>QUADRANGLE GP INVESTORS LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVEUNE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001281082</rptOwnerCik>
            <rptOwnerName>QUADRANGLE GP INVESTORS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>14TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2005-02-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10666667</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12372496</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1705829</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                    <footnoteId id="F4"/>
                    <footnoteId id="F5"/>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the terms of an exchange agreement dated as of November 12, 2004 by and among Protection One, Inc. (&quot;POI&quot;), Protection One Alarm Monitoring, Inc., POI Acquisition L.L.C. (&quot;POIA&quot;), POI Acquisition I, Inc. and Quadrangle Master Funding Ltd (&quot;QMFL&quot;), the principal balance outstanding under an existing credit facility with POI, the lenders of which were POIA and QMFL, was reduced by $120,000,000 as of February 8, 2005. In consideration for such reduction, POI issued and delivered an aggregate of 16,000,000 shares of common stock of POI, par value $0.01 per share (&quot;Common Stock&quot;), to such lenders, of which POIA received 10,666,667 such shares.</footnote>
        <footnote id="F2">All shares of Common Stock reported herein are owned by POI Acquisition I, Inc.</footnote>
        <footnote id="F3">On February 8, 2005, POI effectuated a one-share-for-fifty shares reverse stock split, resulting in a decrease in the number of shares held by POI Acquisition I, Inc. immediately prior to the reverse stock split to 1,705,829 shares of Common Stock.  The shares issued to POIA as described in footnote (1) of this form were not affected by the reverse stock split. POIA may be deemed, as a result of its ownership of 66.67% of the total outstanding shares of POI Acquisition I, Inc. to have shared voting or dispositive power with respect to the shares of Common Stock owned by POI Acquisition I, Inc.</footnote>
        <footnote id="F4">Quadrangle GP Investors LP is the general partner of Quadrangle Capital Partners LP, Quadrangle Select Partners LP and Quadrangle Capital Partners-A LP, which together own all of the equity of POIA. Quadrangle GP Investors LLC is the general partner of Quadrangle GP Investors LP.</footnote>
        <footnote id="F5">Beneficial ownership of the shares of Common Stock referred to herein is being reported hereunder by Quadrangle Capital Partners LP, Quadrangle Select Partners LP, Quadrangle Capital Partners-A LP, Quadrangle GP Investors LP and Quadrangle GP Investors LLC solely because such reporting persons may be deemed to share beneficial ownership of such shares as a result of their respective relationship to POIA and POI Acquisition I, Inc.</footnote>
        <footnote id="F6">Beneficial ownership of the shares of Common Stock referred to herein is being reported hereunder by POIA solely because such reporting person may be deemed to share beneficial ownership of such shares as a result of their respective relationship to POI Acquisition I, Inc. However, POIA disclaims beneficial ownership of the shares of Common Stock beneficially owned by POI Acquisition I, Inc., except to the extent of any pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ David A. Tanner, Manager of POI Acquisition, L.L.C. (see signatures of other reporting persons attached as Exhibit 99)</signatureName>
        <signatureDate>2005-02-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
