| Document and Entity Information | Dec. 13, 2023 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001826892 |
| Document Type | 8-K |
| Document Period End Date | Dec. 13, 2023 |
| Entity Registrant Name | BIOATLA, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39787 |
| Entity Tax Identification Number | 85-1922320 |
| Entity Address, Address Line One | 11085 Torreyana Road |
| Entity Address, City or Town | San Diego |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92121 |
| City Area Code | 858 |
| Local Phone Number | 558-0708 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.0001 par value per share |
| Trading Symbol | BCAB |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
