Additions
| from | Name | Pos | Team | Team | ||
|---|---|---|---|---|---|---|
| 07/2012 |  | Artabe | DF | |||
| 07/2012 | | Markel Etxeberria | DF | |||
| 07/2012 | | Aitor Seguín | MF |  | Athletic Club | Athletic |
| 07/2012 | | Bengoa | MF |  | Athletic Club U19 | Bilbao U19 |
| 07/2012 | | Iker Undabarrena | MF | |||
| 07/2012 | | Iñigo Lekue | MF | |||
| 07/2012 | | Unai López | MF | |||
| 07/2012 | | Gorka Santamaría | FW | | Athletic Club U19 | Bilbao U19 |
| 07/2012 | | Sabin | FW |  | Athletic Club B | Bilbao B |
| 07/2012 |  | Víctor Monteiro | FW | | Athletic Club U19 | Bilbao U19 |
Departures
| from | Name | Pos | Team | Team | ||
|---|---|---|---|---|---|---|
| 02/2013 | | Kepa | GK | | Athletic Club B | Bilbao B |
| 07/2012 | | Aymeric Laporte | DF | | Athletic Club B | Bilbao B |
| 07/2012 | | Aketxe | MF | | Athletic Club B | Bilbao B |
| 07/2012 | | Iker Guarrotxena | MF | | Athletic Club B | Bilbao B |
| 07/2012 | | Jon Iru | MF |  | Sestao River | Sestao River |
| 07/2012 | | Magdaleno | MF | | Athletic Club B | Bilbao B |
| 07/2012 | | Sergio Mendigutxia | FW |  | La Roda CF | La Roda |