| Document and Entity Information | Aug. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 12, 2021 |
| Entity Registrant Name | Nkarta, Inc. |
| Entity Central Index Key | 0001787400 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Entity File Number | 001-39370 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 47-4515206 |
| Entity Address, Address Line One | 6000 Shoreline Court |
| Entity Address, Address Line Two | Suite 102 |
| Entity Address, City or Town | South San Francisco |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94080 |
| City Area Code | 415 |
| Local Phone Number | 582-4923 |
| 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 | NKTX |
| Security Exchange Name | NASDAQ |
