Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	May 04, 2023
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Entity Registrant Name	Sensei Biotherapeutics, Inc.
Entity Central Index Key	0001829802
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		30,980,841
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-39980
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1863385
Entity Address, Address Line One	1405 Research Blvd
Entity Address, Address Line Two	Suite 125
Entity Address, City or Town	Rockville
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20850
City Area Code	240
Local Phone Number	243-8000
Document Quarterly Report	true
Document Transition Report	false
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	SNSE
Security Exchange Name	NASDAQ
Series A Preferred Stock Purchase Rights
Document Information [Line Items]
Title of 12(b) Security	Series A Preferred Stock Purchase Rights
No Trading Symbol Flag	true
Security Exchange Name	NASDAQ