<SEC-DOCUMENT>0001209191-20-021113.txt : 20200325
<SEC-HEADER>0001209191-20-021113.hdr.sgml : 20200325
<ACCEPTANCE-DATETIME>20200325163425
ACCESSION NUMBER:		0001209191-20-021113
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20200323
FILED AS OF DATE:		20200325
DATE AS OF CHANGE:		20200325

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			AMERICAN INTERNATIONAL GROUP INC
		CENTRAL INDEX KEY:			0000005272
		STANDARD INDUSTRIAL CLASSIFICATION:	FIRE, MARINE & CASUALTY INSURANCE [6331]
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	811-22546
		FILM NUMBER:		20742529

	BUSINESS ADDRESS:	
		STREET 1:		175 WATER STREET
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10038
		BUSINESS PHONE:		2127707000

	MAIL ADDRESS:	
		STREET 1:		175 WATER STREET
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10038

	FORMER NAME:	
		FORMER CONFORMED NAME:	AMERICAN INTERNATIONAL ENTERPRISES INC
		DATE OF NAME CHANGE:	19700507

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ClearBridge Energy Midstream Opportunity Fund Inc.
		CENTRAL INDEX KEY:			0001517518
		IRS NUMBER:				451474578
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		620 EIGHTH AVENUE
		STREET 2:		49TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10018
		BUSINESS PHONE:		888-777-0102

	MAIL ADDRESS:	
		STREET 1:		620 EIGHTH AVENUE
		STREET 2:		49TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10018

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ClearBridge Energy MLP Opportunity Fund Inc.
		DATE OF NAME CHANGE:	20110406
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2020-03-23</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001517518</issuerCik>
        <issuerName>ClearBridge Energy Midstream Opportunity Fund Inc.</issuerName>
        <issuerTradingSymbol>EMO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000005272</rptOwnerCik>
            <rptOwnerName>AMERICAN INTERNATIONAL GROUP INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>175 WATER STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10038</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>4.51% Series G Senior Secured Notes due October 15, 2023</value>
            </securityTitle>
            <transactionDate>
                <value>2020-03-23</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>7690817.66</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7996865.19</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>9196650.26</value>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held through subsidiaries</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>4.66% Series H Senior Secured Notes due October 15, 2025</value>
            </securityTitle>
            <transactionDate>
                <value>2020-03-23</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>10312194.95</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10729346.16</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <valueOwnedFollowingTransaction>
                    <value>12331283.31</value>
                </valueOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Held through subsidiaries</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The reported disposition was pursuant to a partial prepayment by the issuer at a price equal to the face value of the prepaid securities, plus accrued and unpaid interest, plus a pro rata portion of the make-whole amount with respect to the principal, calculated in accordance with the note purchase agreement, dated as of October 15, 2013.</footnote>
        <footnote id="F2">American General Life Insurance Company (&quot;AGLIC&quot;) and American Home Assurance Company (&quot;AHAC&quot;), each an indirect wholly owned subsidiary of AIG, directly hold $6,276,713.87 principal amount and $2,919,936.49 principal amount, respectively, of the 4.51% Series G Senior Secured Notes due October 15, 2023 (the &quot;Series G Notes&quot;). AIG is an indirect beneficial owner of the Series G Notes.</footnote>
        <footnote id="F3">AGLIC, AHAC, The United States Life Insurance Company in The City of New York (&quot;USLIC&quot;) and The Variable Annuity Life Insurance Company (&quot;VALIC&quot;), each an indirect wholly owned subsidiary of AIG, directly held $1,633,895.04 principal amount, $3,915,182.45 principal amount, $1,233,128.33 principal amount and $5,549,077.49 principal amount, respectively, of the 4.66% Series H Senior Secured Notes due October 15, 2025 (the &quot;Series H Notes&quot;). AIG is an indirect beneficial owner of the Series H Notes.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Geoffrey N. Cornell, Authorized Signatory of American International Group, Inc.</signatureName>
        <signatureDate>2020-03-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
