The Asturian executive will work within the scouting structure at the Premier League champions and Champions League runners-up, having already begun his new role following a quiet internal appointment.
Alonso's arrival is backed by Andrea Berta, Arsenal's sporting director, with the pair having built a close relationship during five years working together at Atletico Madrid between 2016 and 2021. That bond endured even after Alonso left to join Granada alongside his friend Matteo Tognozzi in 2023, when the club were still in the top flight.
At Granada, Alonso contributed his knowledge of international football during Tognozzi's time as sporting director. His future looked uncertain following the Italian's dismissal, but he spent the past year and a half sharing recruitment duties with Miguel Melgar, who was responsible for scouting, and pushed hard for the club to back young talent such as Oscar Naasei among others.
At Arsenal, Alonso will work alongside Maurizio Micheli, formerly of Napoli, as the club looks to identify emerging talent with a direct line to head coach Mikel Arteta. Arsenal have already been linked with Argentina forward Julian Alvarez, who has made clear his desire to leave Atletico Madrid - the club that signed him with Berta as sporting director.
Before his time at Atletico, Alonso worked in youth coaching at Sporting Gijon, his hometown club, and had a spell as a scout for Sassuolo in Italy. His appointment continues a period of significant behind-the-scenes investment at Arsenal since Berta's arrival earlier this year, with the club building out an extensive scouting network to complement Arteta's coaching staff.
Granada, who Alonso leaves after two and a half years, are now working with a reduced squad as they continue preparations for the new season, with his departure representing a notable loss for a club already navigating a difficult summer in the transfer market.