| Cover Page | Nov. 04, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 4, 2020 |
| Entity Registrant Name | Mistras Group, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-34481 |
| Entity Tax Identification Number | 22-3341267 |
| Entity Address, Address Line One | 195 Clarksville Road |
| Entity Address, Postal Zip Code | 08550 |
| Entity Address, City or Town | Princeton Junction, |
| Entity Address, State or Province | NJ |
| City Area Code | 609 |
| Local Phone Number | 716-4000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.01 par value |
| Trading Symbol | MG |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001436126 |
| Amendment Flag | false |
