| Cover | May 07, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | May 7, 2021 |
| Entity Registrant Name | BLACK DIAMOND THERAPEUTICS, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39200 |
| Entity Tax Identification Number | 81-4254660 |
| Entity Address, Address Line One | One Main Street, 10th Floor |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.0001 par value per share |
| Trading Symbol | BDTX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001701541 |
| Amendment Flag | false |
