Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 16, 2020	Feb. 03, 2020
Cover page.
Document Type	10-K
Entity Registrant Name	BLACK DIAMOND THERAPEUTICS, INC.
Document Annual Report	true
Document Transition Report	false
Entity File Number	001-38501
Entity Central Index Key	0001701541
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4254660
Title of 12(b) Security	Common stock, par value $0.0001
Trading Symbol	BDTX
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Shell Company	false
Entity Current Reporting Status	Yes
Amendment Flag	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Address, Address Line One	139 Main Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	(617)
Local Phone Number	252-0848
Entity Public Float			$ 910,076,402
Entity Common Stock, Shares Outstanding		35,910,705
Documents Incorporated by Reference	None.