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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-09-24</periodOfReport>

    <issuer>
        <issuerCik>0000866873</issuerCik>
        <issuerName>DEL MONTE FOODS CO</issuerName>
        <issuerTradingSymbol>DLM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001466869</rptOwnerCik>
            <rptOwnerName>BODNER LARRY E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>PO BOX 193575</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94119</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>SVP, Finance &amp; Inv. Relations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.01, Par Value</value>
            </securityTitle>
            <transactionDate>
                <value>2009-09-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10900</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>64393</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (right To Purchase)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.40</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-09-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>91100</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-09-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.01, Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>91100</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>91100</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance Share</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-09-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>27300</value>
                    <footnoteId id="F5"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F7"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, $0.01, Par Value</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>27300</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>86550</value>
                    <footnoteId id="F8"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Performance Accelerated Restricted Stock Units that generally vest 100% on the fifth anniversary of the transaction date; vesting may be accelerated if certain performance milestones are met.</footnote>
        <footnote id="F2">This entry reflects the grant of Performance Accelerated Restricted Stock Units and accordingly the price is left blank.</footnote>
        <footnote id="F3">Options generally vest 25% per year for four (4) years beginning with the first anniversary of the transaction date.</footnote>
        <footnote id="F4">1 performance share unit for 1 share of common stock.</footnote>
        <footnote id="F5">Represents maximum number of shares of common stock which may be earned in connection with the 9/24/09 grant of performance share units.  The target number of shares associated with the grant is 18,200.</footnote>
        <footnote id="F6">Vesting of performance share units is based on the Company's level of achievement of Relative Total Shareholder Return (RTSR) over the performance period.</footnote>
        <footnote id="F7">Performance share units either vest or forfeit based on the Company's level of achievement of RTSR over the performance period.  Because vesting of the performance share units is tied to a performance measure that is not solely the Company's stock price (due to the impact of Company dividends and comparator group performance on RTSR), the performance share units may not currently be considered &quot;derivative securities&quot; under applicable rules and accordingly, to such extent, the Reporting Person may be considered to have reported these performance share units voluntarily.</footnote>
        <footnote id="F8">Includes performance share units previously reported voluntarily with different vesting terms.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James Potter, signed pursuant to power of attorney</signatureName>
        <signatureDate>2009-09-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
