Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 24, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Entity File Number	001-38916
Entity Registrant Name	BICYCLE THERAPEUTICS PLC
Entity Incorporation, State or Country Code	X0
Entity Tax Identification Number	00-0000000
Entity Address, Address Line One	B900
Entity Address, Address Line Two	Babraham Research Campus
Entity Address, City or Town	Cambridge
Entity Address, Country	GB
Entity Address, Postal Zip Code	CB22 3AT
City Area Code	+44
Local Phone Number	1223 261503
Entity Filer Category	Large Accelerated Filer
Entity Voluntary Filers	No
Entity Well Known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		29,598,616
Entity Public Float			$ 717,602,531
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001761612
Amendment Flag	false
ICFR Auditor Attestation Flag	true
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	876
Auditor Location	Cambridge, United Kingdom
Ordinary Shares
Document Information [Line Items]
Title of 12(b) Security	Ordinary shares, nominal value £0.01 per share*
No Trading Symbol Flag	true
Security Exchange Name	NASDAQ
American Depositary Shares
Document Information [Line Items]
Title of 12(b) Security	American Depositary Shares, each representing one ordinary share, nominal value £0.01 per share
Trading Symbol	BCYC
Security Exchange Name	NASDAQ