| Document and Entity Information | Oct. 26, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Entity Central Index Key | 0001069308 |
| Document Period End Date | Oct. 26, 2021 |
| Entity Registrant Name | ACER THERAPEUTICS INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-33004 |
| Entity Tax Identification Number | 32-0426967 |
| Entity Address, Address Line One | One Gateway Center |
| Entity Address, Address Line Two | Suite 351 |
| Entity Address, Address Line Three | 300 Washington Street |
| Entity Address, City or Town | Newton |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02458 |
| City Area Code | 844 |
| Local Phone Number | 902-6100 |
| 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 | ACER |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
