| 02 Sept 19 | A. Alese Ajibola Alese |  West Ham UnitedWHU | → |  Accrington StanleyACCR | Loan |
| 02 Sept 19 | J. Hernández Javier Hernández | West Ham UnitedWHU | → |  SevillaSEV | Undisclosed |
| 02 Sept 19 | J. Hernández Javier Hernández | West Ham UnitedWHU | → | SevillaSEV | Undisclosed |
| 29 Aug 19 | O. Afolayan Oladapo Afolayan | West Ham UnitedWHU | → |  Mansfield TownMAN | Loan |
| 08 Aug 19 | A. Ajeti Albian Ajeti |  FC BaselBAS | → | West Ham UnitedWHU | Undisclosed |
| 08 Aug 19 | G. Diangana Grady Diangana | West Ham UnitedWHU | → |  West Bromwich AlbionWBA | Loan |
| 08 Aug 19 | G. Diangana Grady Diangana | West Ham UnitedWHU | → | West Bromwich AlbionWBA | Loan |
| 07 Aug 19 | J. Cullen Josh Cullen | West Ham UnitedWHU | → |  Charlton AthleticCHA | Loan |
| 07 Aug 19 | J. Cullen Josh Cullen | West Ham UnitedWHU | → | Charlton AthleticCHA | Loan |
| 06 Aug 19 | G. Cardoso Gonçalo Cardoso |  BoavistaBOA | → | West Ham UnitedWHU | Undisclosed |
| 02 Aug 19 | R. Oxford Reece Oxford | West Ham UnitedWHU | → |  FC AugsburgAUG | Undisclosed |
| 02 Aug 19 | R. Oxford Reece Oxford | West Ham UnitedWHU | → | FC AugsburgAUG | Undisclosed |
| 28 Jul 19 | J. Hugill Jordan Hugill | West Ham UnitedWHU | → |  Queens Park RangersQPR | Loan |
| 28 Jul 19 | J. Hugill Jordan Hugill | West Ham UnitedWHU | → | Queens Park RangersQPR | Loan |
| 26 Jul 19 | M. Browne Marcus Browne | West Ham UnitedWHU | → |  MiddlesbroughMID | Undisclosed |
| 26 Jul 19 | M. Browne Marcus Browne | West Ham UnitedWHU | → | MiddlesbroughMID | Undisclosed |
| 24 Jul 19 | P. Obiang Pedro Obiang | West Ham UnitedWHU | → |  SassuoloSAS | Undisclosed |
| 24 Jul 19 | P. Obiang Pedro Obiang | West Ham UnitedWHU | → | SassuoloSAS | Undisclosed |
| 17 Jul 19 | S. Haller Sébastien Haller |  Eintracht FrankfurtSGE | → | West Ham UnitedWHU | Undisclosed |
| 17 Jul 19 | S. Haller Sébastien Haller | Eintracht FrankfurtSGE | → | West Ham UnitedWHU | Undisclosed |
| 16 Jul 19 | S. Byram Sam Byram | West Ham UnitedWHU | → |  Norwich CityNOR | Undisclosed |
| 08 Jul 19 | M. Arnautovic Marko Arnautovic | West Ham UnitedWHU | → |  Shanghai PortSIPG | Undisclosed |
| 05 Jul 19 | S. Nasri Samir Nasri | West Ham UnitedWHU | → |  AnderlechtAND | Free |
| 01 Jul 19 | D. Martin David Martin |  MillwallMIL | → | West Ham UnitedWHU | Free |
| 01 Jul 19 | N. Trott Nathan Trott | West Ham UnitedWHU | → |  Northampton TownNHT | Loan |
| 01 Jul 19 | Roberto |  EspanyolESP | → | West Ham UnitedWHU | Free |
| 01 Jul 19 | L. Pérez Lucas Pérez | West Ham UnitedWHU | → |  AlavésALV | Undisclosed |
| 01 Jul 19 | E. Fernandes Edimilson Fernandes | West Ham UnitedWHU | → |  MainzMAIN | Undisclosed |
| 01 Jul 19 | D. Martin David Martin | MillwallMIL | → | West Ham UnitedWHU | Free |
| 01 Jul 19 | L. Pérez Lucas Pérez | West Ham UnitedWHU | → | AlavésALV | Undisclosed |
| 01 Jul 19 | Roberto | EspanyolESP | → | West Ham UnitedWHU | Free |
| 01 Jul 19 | E. Fernandes Edimilson Fernandes | West Ham UnitedWHU | → | MainzMAIN | Undisclosed |
| 14 Jun 19 | P. Fornals Pablo Fornals |  VillarrealVIL | → | West Ham UnitedWHU | Undisclosed |
| 14 Jun 19 | P. Fornals Pablo Fornals | VillarrealVIL | → | West Ham UnitedWHU | Undisclosed |
| 31 Jan 19 | R. Oxford Reece Oxford | West Ham UnitedWHU | → | FC AugsburgAUG | Loan |
| 31 Jan 19 | R. Oxford Reece Oxford | West Ham UnitedWHU | → | FC AugsburgAUG | Loan |
| 30 Jan 19 | Mesaque Dju |  BenficaBEN | → | West Ham UnitedWHU | Free |
| 21 Jan 19 | Joe Powell | West Ham UnitedWHU | → | Northampton TownNHT | Loan |
| 11 Jan 19 | M. Makasi Moses Makasi | West Ham UnitedWHU | → |  StevenageSTE | Loan |
| 04 Jan 19 | V. Neufville Vashon Neufville | West Ham UnitedWHU | → |  Newport CountyNEW | Loan |
| 01 Jan 19 | S. Nasri Samir Nasri | XXX | → | West Ham UnitedWHU | Free |