| Cover | Jun. 28, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jun. 28, 2021 |
| Entity Registrant Name | Cardiff Oncology, Inc. |
| Entity File Number | 001-35558 |
| Entity Tax Identification Number | 27-2004382 |
| Entity Address, Address Line One | 11055 Flintkote Avenue |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92121 |
| Entity Address, City or Town | San Diego |
| City Area Code | (858) |
| Local Phone Number | 952-7570 |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | CRDF |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Incorporation, State or Country Code | DE |
| Entity Central Index Key | 0001213037 |
| Amendment Flag | false |
| Security Exchange Name | NASDAQ |
