| 1. Round | 18/10/2020 | Real Sociedad B | - | SD Leioa | 1:0 | ||||
| 3. Round | 01/11/2020 | Real Sociedad B | - | CD Laredo | 3:0 | ||||
| 7. Round | 29/11/2020 | Arenas de Getxo | - | Real Sociedad B | 1:1 | ||||
| 9. Round | 12/12/2020 | Club Portugalete | - | Real Sociedad B | 1:1 | ||||
| 14. Round | 31/01/2021 | CD Laredo | - | Real Sociedad B | 0:0 | ||||
| 15. Round | 07/02/2021 | Real Sociedad B | - | Barakaldo CF | 2:0 | ||||
| 17. Round | 20/02/2021 | Real Unión | - | Real Sociedad B | 3:1 |  |
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| 18. Round | 28/02/2021 | Real Sociedad B | - | Arenas de Getxo | 3:0 |  |
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| 19. Round | 07/03/2021 | Racing Santander | - | Real Sociedad B | 0:1 | ||||
| 20. Round | 14/03/2021 | Real Sociedad B | - | Club Portugalete | 2:0 | ||||
| 21. Round | 21/03/2021 | Athletic Club B | - | Real Sociedad B | 1:2 | ||||
| 22. Round | 28/03/2021 | Real Sociedad B | - | CD Alavés B | 4:1 |
Spain