Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 02, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Transition Report	false
Entity File Number	001-38550
Document Quarterly Report	true
Entity Registrant Name	Translate Bio, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	61-1807780
Entity Address, Address Line One	29 Hartwell Avenue
Entity Address, City or Town	Lexington
Entity Address, Postal Zip Code	02421
Trading Symbol	TBIO
City Area Code	617
Local Phone Number	945-7361
Entity Central Index Key	0001693415
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Title of 12(b) Security	Common Stock
Entity Address, State or Province	MA
Entity Interactive Data Current	Yes
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		75,586,714