Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 10, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K/A
Amendment Flag	true
Amendment Description	Amendment No. 1
Entity Shell Company	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	ACET
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Entity Registrant Name	Adicet Bio, Inc.
Entity Central Index Key	0001720580
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		31,780,347
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-38359
Entity Tax Identification Number	81-3305277
Entity Public Float			$ 40.0
Entity Address, Address Line One	200 Clarendon Street
Entity Address, Address Line Two	Floor 6
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
Entity Incorporation, State or Country Code	DE
City Area Code	857
Local Phone Number	315-5528
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false