| 16 Oct 20 | S. Benrahma Saïd Benrahma |  BrentfordBRE | → |  West Ham UnitedWHU | Loan |
| 16 Oct 20 | S. Benrahma Saïd Benrahma | BrentfordBRE | → | West Ham UnitedWHU | Loan |
| 12 Oct 20 | C. Dawson Craig Dawson |  WatfordWAT | → | West Ham UnitedWHU | Loan |
| 12 Oct 20 | C. Dawson Craig Dawson | WatfordWAT | → | West Ham UnitedWHU | Loan |
| 06 Oct 20 | Felipe Anderson | West Ham UnitedWHU | → |  FC PortoPOR | Loan |
| 05 Oct 20 | J. Cullen Josh Cullen | West Ham UnitedWHU | → |  AnderlechtAND | Undisclosed |
| 05 Oct 20 | X. Silva Xande Silva | West Ham UnitedWHU | → |  ArisARI | Loan |
| 02 Oct 20 | V. Coufal Vladimír Coufal | SPXSlavia PragueSlavia Prague | → | West Ham UnitedWHU | Undisclosed |
| 04 Sept 20 | G. Diangana Grady Diangana | West Ham UnitedWHU | → |  West Bromwich AlbionWBA | Undisclosed |
| 03 Sept 20 | D. Kemp Daniel Kemp | West Ham UnitedWHU | → |  BlackpoolBLP | Loan |
| 28 Aug 20 | Roberto | West Ham UnitedWHU | → |  Real ValladolidVLL | Undisclosed |
| 28 Aug 20 | Roberto | West Ham UnitedWHU | → | Real ValladolidVLL | Undisclosed |
| 24 Aug 20 | J. Hugill Jordan Hugill | West Ham UnitedWHU | → |  Norwich CityNOR | Undisclosed |
| 24 Aug 20 | J. Hugill Jordan Hugill | West Ham UnitedWHU | → | Norwich CityNOR | Undisclosed |
| 13 Aug 20 | A. Ajeti Albian Ajeti | West Ham UnitedWHU | → |  CelticCEL | Undisclosed |
| 13 Aug 20 | A. Ajeti Albian Ajeti | West Ham UnitedWHU | → | CelticCEL | Undisclosed |
| 24 Jul 20 | T. Soucek Tomás Soucek | SPXSlavia PragueSlavia Prague | → | West Ham UnitedWHU | Undisclosed |
| 14 Feb 20 | W. Reid Winston Reid | West Ham UnitedWHU | → |  Sporting Kansas CitySKC | Loan |
| 14 Feb 20 | W. Reid Winston Reid | West Ham UnitedWHU | → | Sporting Kansas CitySKC | Loan |
| 31 Jan 20 | J. Bowen Jarrod Bowen |  Hull CityHUL | → | West Ham UnitedWHU | Undisclosed |
| 31 Jan 20 | J. Bowen Jarrod Bowen | Hull CityHUL | → | West Ham UnitedWHU | Undisclosed |
| 31 Jan 20 | D. Kemp Daniel Kemp | West Ham UnitedWHU | → |  StevenageSTE | Loan |
| 29 Jan 20 | T. Soucek Tomás Soucek | SPXSlavia PragueSlavia Prague | → | West Ham UnitedWHU | Loan |
| 20 Jan 20 | Roberto | West Ham UnitedWHU | → |  AlavésALV | Loan |
| 20 Jan 20 | Roberto | West Ham UnitedWHU | → | AlavésALV | Loan |
| 16 Jan 20 | M. Samuelsen Martin Samuelsen | West Ham UnitedWHU | → | Hull CityHUL | Undisclosed |
| 16 Jan 20 | M. Samuelsen Martin Samuelsen | West Ham UnitedWHU | → | Hull CityHUL | Undisclosed |
| 15 Jan 20 | D. Randolph Darren Randolph |  MiddlesbroughMID | → | West Ham UnitedWHU | Undisclosed |
| 15 Jan 20 | D. Randolph Darren Randolph | MiddlesbroughMID | → | West Ham UnitedWHU | Undisclosed |
| 14 Jan 20 | J. Powell Joe Powell | West Ham UnitedWHU | → |  Burton AlbionBRT | Undisclosed |
| 10 Jan 20 | C. Coventry Conor Coventry | West Ham UnitedWHU | → |  Lincoln CityLCN | Loan |
| 08 Jan 20 | N. Holland Nathan Holland | West Ham UnitedWHU | → |  Oxford UnitedOXF | Loan |