| 3. Round | 01/11/2020 | Club Portugalete | - | Athletic Club B | 2:3 | ||||
| 4. Round | 07/11/2020 | Athletic Club B | - | SD Amorebieta | 2:1 | ||||
| 5. Round | 14/11/2020 | Athletic Club B | - | CD Alavés B | 2:0 | ||||
| 6. Round | 22/11/2020 | SD Leioa | - | Athletic Club B | 1:1 | ||||
| 8. Round | 05/12/2020 | CD Laredo | - | Athletic Club B | 2:2 |  |
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| 10. Round | 19/12/2020 | Real Sociedad B | - | Athletic Club B | 1:2 | ||||
| 20. Round | 14/03/2021 | Barakaldo CF | - | Athletic Club B | 3:1 | ||||
| 17. Round | 17/03/2021 | Athletic Club B | - | SD Leioa | 4:0 | ||||
| 21. Round | 21/03/2021 | Athletic Club B | - | Real Sociedad B | 1:2 |  |
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| 22. Round | 28/03/2021 | Real Unión | - | Athletic Club B | 0:1 |
Spain