| 4. Round | 15/09/2018 | SD Leioa | - | Athletic Club B | 1:4 | ||||
| 5. Round | 22/09/2018 | Athletic Club B | - | SD Gernika | 3:0 | ||||
| 6. Round | 29/09/2018 | Real Oviedo B | - | Athletic Club B | 2:1 |  |
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| 7. Round | 06/10/2018 | Athletic Club B | - | UD Logroñés | 0:0 | ||||
| 8. Round | 13/10/2018 | Real Sociedad B | - | Athletic Club B | 1:0 | |
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| 9. Round | 20/10/2018 | Athletic Club B | - | CD Mirandés | 1:3 | ||||
| 10. Round | 27/10/2018 | Arenas de Getxo | - | Athletic Club B | 1:0 | ||||
| 16. Round | 09/12/2018 | Sporting Gijón B | - | Athletic Club B | 3:1 | ||||
| 17. Round | 15/12/2018 | Athletic Club B | - | CD Calahorra | 3:2 | ||||
| 18. Round | 22/12/2018 | Real Unión | - | Athletic Club B | 1:0 | ||||
| 19. Round | 05/01/2019 | Athletic Club B | - | CD Vitoria | 2:0 | ||||
| 20. Round | 13/01/2019 | CD Tudelano | - | Athletic Club B | 3:2 | ||||
| 21. Round | 19/01/2019 | Athletic Club B | - | Gimnástica Torrelavega | 1:0 | ||||
| 35. Round | 28/04/2019 | Athletic Club B | - | Sporting Gijón B | 0:2 | ||||
| 36. Round | 05/05/2019 | CD Calahorra | - | Athletic Club B | 0:3 | ||||
| 37. Round | 12/05/2019 | Athletic Club B | - | Real Unión | 2:0 | |
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| 38. Round | 19/05/2019 | CD Vitoria | - | Athletic Club B | 0:0 |
Spain