Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	CUE
Entity Registrant Name	Cue Biopharma, Inc.
Entity Central Index Key	0001645460
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Interactive Data Current	Yes
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		31,760,946
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38327
Entity Tax Identification Number	47-3324577
Entity Address, Address Line One	21 Erie Street
Entity Address, City or Town	Cambridge
Entity Address State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	949-2680