<SEC-DOCUMENT>0001084991-21-000013.txt : 20210322
<SEC-HEADER>0001084991-21-000013.hdr.sgml : 20210322
<ACCEPTANCE-DATETIME>20210322153121
ACCESSION NUMBER:		0001084991-21-000013
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210318
FILED AS OF DATE:		20210322
DATE AS OF CHANGE:		20210322

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CHISHOLM JOHN
		CENTRAL INDEX KEY:			0001173236

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31398
		FILM NUMBER:		21761213

	MAIL ADDRESS:	
		STREET 1:		C/O FLOTEK INDUSTRIES, INC.
		STREET 2:		2930 W. SAM HOUSTON PARKWAY N., STE. 300
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77043

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATURAL GAS SERVICES GROUP INC
		CENTRAL INDEX KEY:			0001084991
		STANDARD INDUSTRIAL CLASSIFICATION:	OIL, GAS FIELD SERVICES, NBC [1389]
		IRS NUMBER:				752811855
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		404 VETERANS AIRPARK LANE
		STREET 2:		SUITE 300
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79705
		BUSINESS PHONE:		(432) 262-2700

	MAIL ADDRESS:	
		STREET 1:		404 VETERANS AIRPARK LANE
		STREET 2:		SUITE 300
		CITY:			MIDLAND
		STATE:			TX
		ZIP:			79705
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-03-18</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001084991</issuerCik>
        <issuerName>NATURAL GAS SERVICES GROUP INC</issuerName>
        <issuerTradingSymbol>ngs</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001173236</rptOwnerCik>
            <rptOwnerName>CHISHOLM JOHN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>404 VETERANS AIRPARK LANE</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>MIDLAND</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>79705</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-18</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5612</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.91</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26792</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The acquisition reflects an award of Restricted Stock pursuant to the Company's 2019 Equity Incentive Plan. The award vests on the first anniversary of the grant date, subject to accelerated vesting under certain circumstances.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>John M. Chisholm</signatureName>
        <signatureDate>2021-03-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
