| Document and Entity Information | May 10, 2024 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001808865 |
| Document Type | 8-K |
| Document Period End Date | May 10, 2024 |
| Entity Registrant Name | iTeos Therapeutics, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-39401 |
| Entity Tax Identification Number | 84-3365066 |
| Entity Address, Address Line One | 321 Arsenal Street |
| Entity Address, City or Town | Watertown |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02472 |
| City Area Code | (339) |
| Local Phone Number | 217 0161 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.001 par value per share |
| Trading Symbol | ITOS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
