The 2025–26 season will mark Osasuna Promesas' fourth consecutive campaign in the Primera Federación. Head coach Santi Castillejo will remain at the helm of the club's top reserve side, which, during this period, has been one of only five reserve teams to consistently compete across Spain's top three divisions, alongside those of Real Madrid, Villarreal, Real Sociedad, and Celta Vigo.

As part of the club's continued focus on player development, seven players from the club's second reserve team, Subiza, will be promoted to the Promesas squad: goalkeeper Rafa Fernández; defenders Álex Jiménez and Asier Larrión; midfielders Aimar Bonel, Miguel Auría, and Bruno Pérez; and forward Asier Bonel. These additions follow the midseason promotions of defender Unai Santos and forward Martín Pedroarena during the previous campaign, underscoring a significant generational transition within the squad.

Several players will return to the team after renewing their contracts. Goalkeeper Dimitros Stamatakis has signed a new deal through June 30, 2027, with the club holding the option to extend the agreement for two additional seasons. Team captain defender Ibaider Garriz, a key leadership figure in a young squad, has also renewed for one more year. In addition, Fernández has extended his contract through 2027, while forward Dani González—who missed the 2024–25 season due to an ACL injury—has signed a one-year extension, with the club retaining the option to extend the deal for two further years.

The following players remain under contract and will continue to hold Osasuna Promesas registrations, pending future decisions by the new senior team coaching staff: defenders Iñigo Arguibide, Diego Moreno, Diego Espejo, and Santos; midfielders Mauro Echegoyen, Asier Osambela, and Jon García; and forwards Roberto Arroyo, Pedroarena, Anai Morales, and Carlos Lumbreras.

Several players will depart after concluding their contractual obligations with the club. Among them are academy standouts midfielder Xabi Huarte; goalkeeper Pablo Valencia; forwards Nowend Lorenzo, Dani Sancho; and defender Christian Mutilva. Club Atlético Osasuna extends its sincere gratitude for their dedication and service to the organization. The club also thanks defenders Toni Herrero and Isma Sierra, as well as forwards Pablo Moreno and Noel López, whose tenures will also come to an end. In the cases of López and Sierra, the club has opted not to exercise the purchase options on their rights. Meanwhile, Osasuna retains a purchase option on forward Sixtus Ogbuehi through June 30. Finally, the club will not renew defender Jorge Moreno's contract, who spent the past season on loan with FC Cartagena in LaLiga Hypermotion.