Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 Form 10 - K × ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 or For the transition period from to Delaware ( State or other jurisdiction of incorporation or organization ) Commission File Number 001-34481 Mistras Group , Inc. ( Exact name of registrant as specified in its charter ) Large accelerated filer o Non - accelerated filer o Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common Stock , par value $ .01 par value Securities registered pursuant to Section 12 ( g ) of the Act : None 195 Clarksville Road Princeton Junction , New Jersey 08550 ( Address of principal executive offices ) ( Zip Code ) ( 609 ) 716-4000 ( Registrant's telephone number , including area code ) 22-3341267 ( I.R.S. Employer Identification Number ) Trading Symbol MG Name of each exchange on which registered New York Stock Exchange Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes o No ý Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes o No ý Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes ý No o Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes ý No o Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer or a smaller reporting company or an emerging growth company . See the definitions of " large accelerated filer , ” “ accelerated filer ” , “ smaller reporting company " and " emerging growth company " in Rule 12b - 2 of the Exchange Act .: Accelerated filer Smaller reporting company Emerging growth company × 00 X