| Document and Entity Information | Nov. 09, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 9, 2021 |
| Entity Registrant Name | TransMedics Group, Inc. |
| Entity Central Index Key | 0001756262 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity File Number | 001-38891 |
| Entity Incorporation, State or Country Code | MA |
| Entity Tax Identification Number | 83-2181531 |
| Entity Address, Address Line One | 200 Minuteman Road |
| Entity Address, City or Town | Andover |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01810 |
| City Area Code | (978) |
| Local Phone Number | 552-0900 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, no par value per share |
| Trading Symbol | TMDX |
| Security Exchange Name | NASDAQ |
