| Cover | Mar. 09, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Aug. 04, 2022 |
| Entity Registrant Name | Keros Therapeutics, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39264 |
| Entity Tax Identification Number | 81-1173868 |
| Entity Address, Address Line One | 99 Hayden Avenue |
| Entity Address, Address Line Two | Suite 120 |
| Entity Address, Address Line Three | Building E |
| Entity Address, City or Town | Lexington |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02421 |
| City Area Code | 617 |
| Local Phone Number | 314-6297 |
| 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 | KROS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001664710 |
| Amendment Flag | false |
