| Document and Entity Information | Nov. 24, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001720580 |
| Document Type | 8-K |
| Document Period End Date | Nov. 24, 2020 |
| Entity Registrant Name | Adicet Bio, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38359 |
| Entity Tax Identification Number | 81-3305277 |
| Entity Address, Address Line One | 500 Boylston Street |
| Entity Address, Address Line Two | 13th Floor |
| Entity Address, City or Town | Boston |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02116 |
| City Area Code | (857) |
| Local Phone Number | 315-5528 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.0001 per share |
| Trading Symbol | ACET |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
