Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 13, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2022
Current Fiscal Year End Date	--12-31
Entity Registrant Name	IO Biotech, Inc.
Entity Central Index Key	0001865494
Entity File Number	001-41008
Entity Tax Identification Number	87-0909276
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	Ole Maaløes Vej 3
Entity Address, City or Town	Copenhagen N
Entity Address, Country	DK
Entity Address, Postal Zip Code	DK-2200
City Area Code	+45
Local Phone Number	7070 2980
Title of each class	Common Stock, par value $0.001 per share
Trading Symbol(s)	IOBT
Name of each exchange on which registered	NASDAQ
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		28,815,267
Document Quarterly Report	true
Document Transition Report	false