| 01 Sept 23 | K. Appiah-Forson Keenan Appiah-Forson |  West Ham UnitedWHU | → |  Dagenham & RedbridgeD&R | Loan |
| 27 Aug 23 | M. Kudus Mohammed Kudus |  Ajax AmsterdamAJA | → | West Ham UnitedWHU | 43000000 |
| 22 Aug 23 | K. Mavropanos Konstantinos Mavropanos |  VfB StuttgartVFB | → | West Ham UnitedWHU | Undisclosed |
| 21 Aug 23 | F. Downes Flynn Downes | West Ham UnitedWHU | → |  SouthamptonSOU | Loan |
| 14 Aug 23 | J. Ward-Prowse James Ward-Prowse | SouthamptonSOU | → | West Ham UnitedWHU | Undisclosed |
| 10 Aug 23 | E. Álvarez Edson Álvarez | Ajax AmsterdamAJA | → | West Ham UnitedWHU | 38000000 |
| 08 Aug 23 | N. Vlasic Nikola Vlasic | West Ham UnitedWHU | → |  TorinoTOR | Undisclosed |
| 07 Aug 23 | G. Scamacca Gianluca Scamacca | West Ham UnitedWHU | → |  AtalantaATA | Undisclosed |
| 29 Jul 23 | K. Simon-Swyer Kamarai Simon-Swyer | West Ham UnitedWHU | → |  Crawley TownCRA | Loan |
| 28 Jul 23 | F. Potts Freddie Potts | West Ham UnitedWHU | → |  Wycombe WanderersWYC | Loan |
| 15 Jul 23 | D. Rice Declan Rice | West Ham UnitedWHU | → |  ArsenalARS | Undisclosed |
| 01 Jul 23 | A. Masuaku Arthur Masuaku | West Ham UnitedWHU | → |  BesiktasBES | Undisclosed |
| 31 Jan 23 | H. Ashby Harrison Ashby | West Ham UnitedWHU | → |  Newcastle UnitedNEW | Undisclosed |
| 31 Jan 23 | E. Longelo Emmanuel Longelo | West Ham UnitedWHU | → |  Birmingham CityBIR | Undisclosed |
| 27 Jan 23 | W. Greenidge William Greenidge | West Ham UnitedWHU | → |  Colchester UnitedCOL | Undisclosed |
| 26 Jan 23 | C. Coventry Conor Coventry | West Ham UnitedWHU | → |  Rotherham UnitedROT | Loan |
| 26 Jan 23 | D. Randolph Darren Randolph | West Ham UnitedWHU | → |  AFC BournemouthBOU | Free |
| 23 Jan 23 | P. Ekwah Pierre Ekwah | West Ham UnitedWHU | → |  SunderlandSUN | Undisclosed |
| 22 Jan 23 | C. Dawson Craig Dawson | West Ham UnitedWHU | → |  Wolverhampton WanderersWOL | Undisclosed |
| 20 Jan 23 | D. Ings Danny Ings |  Aston VillaAVL | → | West Ham UnitedWHU | Undisclosed |
| 10 Jan 23 | T. Nevers Thierry Nevers | West Ham UnitedWHU | → |  Bradford CityBRD | Loan |
| 01 Jan 23 | Luizão |  São PauloSAO | → | West Ham UnitedWHU | Undisclosed |