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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-05-04</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001219360</issuerCik>
        <issuerName>PIMCO HIGH INCOME FUND</issuerName>
        <issuerTradingSymbol>PHK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001201920</rptOwnerCik>
            <rptOwnerName>KENNEDY RAYMOND G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1345 AVENUE OF AMERICAS</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Vice President/Portfolio Mgr.</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Compensation Deferral Account</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-05-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.96</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Compensation Deferral Account</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">A rabbi trust established in connection with the Executive Deferred Compensation Plan of Allianz Dresdner Asset Management of America LLC acquired common shares of beneficial interest in the Issuer for the Compensation Deferral Account maintained for the benefit of Mr. Kennedy after a contribution to the plan made by Pacific Investment Management Company LLC, a subsidiary of Allianz Dresdner Asset Management of America LLC.  The shares are held in the name of the Allianz Dresdner Asset Management Plan of America.</footnote>
        <footnote id="F2">Mr. Kennedy will receive cash in the value of the shares at the time he is eligible to reveive benefits under the Executive Deferred Compensation Plan, unless he instructs the rabbi trust to sell the shares at an earlier date and allocate the proceeds of the sale to a different investment.  Mr. Kennedy is not eligible to receive benefits under the Plan until five years after the plan year in which the contribution was made to his account, or such later date beyond five years as Mr. Kennedy elects.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Brian S. Shlissel, Attorney in fact for Mr. Raymond Kennedy</signatureName>
        <signatureDate>2006-05-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
