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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2020-02-11</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001293613</issuerCik>
        <issuerName>Kayne Anderson MLP/Midstream Investment Co</issuerName>
        <issuerTradingSymbol>KYN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001137774</rptOwnerCik>
            <rptOwnerName>PRUDENTIAL FINANCIAL INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>751 BROAD ST</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEWARK</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07102</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001444597</rptOwnerCik>
            <rptOwnerName>Prudential Retirement Insurance &amp; Annuity Co</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>prudentail retirement insurance and Annu</rptOwnerStreet1>
            <rptOwnerStreet2>280 Trumbull Street</rptOwnerStreet2>
            <rptOwnerCity>Hartford</rptOwnerCity>
            <rptOwnerState>CT</rptOwnerState>
            <rptOwnerZipCode>06103</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series K Mandatory Redeemable Preferred Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1000000</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Prudential Retirement Insurance and Annuity Company, a wholly-owned subsidiary of the Reporting P</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series L Mandatory Redeemable Preferred Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1200000</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Prudential Retirement Insurance and Annuity Company, a wholly-owned subsidiary of the Reporting P</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>3.26% Series MM Senior Unsecured Notes due October 29, 2022</value>
            </securityTitle>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>1000000</value>
                    <footnoteId id="F4"/>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By The Prudential Insurance Company of America, a wholly-owned subsidiary of the Reporting Person</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>3.26% Series MM Senior Unsecured Notes due October 29, 2022</value>
            </securityTitle>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>12000000</value>
                    <footnoteId id="F4"/>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By The Gibraltar Life Insurance Co., Ltd., a wholly-owned subsidiary of the Reporting Person</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>3.26% Series MM Senior Unsecured Notes due October 29, 2022</value>
            </securityTitle>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>10900000</value>
                    <footnoteId id="F4"/>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Prudential Retirement Insurance and Annuity Company, a wholly-owned subsidiary of the Reporting P</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>3.26% Series MM Senior Unsecured Notes due October 29, 2022</value>
            </securityTitle>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>1100000</value>
                    <footnoteId id="F4"/>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Prudential Arizona Reinsurance Universal Company, a wholly-owned subsidiary of the Reporting Pers</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Acquired on April 10, 2015. Issued by Kayne Anderson Energy Development Company (predecessor by merger to KYN).</footnote>
        <footnote id="F2">Preferred shares owned directly by Prudential Retirement Insurance and Annuity Company, a ten percent owner of a class, and indirectly owned by Prudential Financial, Inc., its parent holding company.</footnote>
        <footnote id="F3">Acquired on February 11, 2020.</footnote>
        <footnote id="F4">Acquired on October 29, 2014.</footnote>
        <footnote id="F5">As grantor of the PAR U Hartford Life Insurance Comfort Trust.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Prudential Financial, Inc. By: /s/Richard Baker, Second Vice President</signatureName>
        <signatureDate>2020-02-13</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Prudential Retirement Insurance and Annuity Company By: PGIM, Inc., as investment manager By: /s/Callie Hamilton, Vice President</signatureName>
        <signatureDate>2020-02-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
