Astralaga joins to compete for the No. 1 shirt at Fernando Torres's side after a season on loan at Granada in Segunda División, where he made 16 appearances and kept three clean sheets. According to the club's official statement, the 22-year-old has signed a two-year deal running until 30 June 2028.
The goalkeeper came through the academies of both Athletic Club and Barcelona, joining the Catalan club from Lezama in 2018 and rising through La Masia to make more than 50 appearances for Barça Atlètic, as well as being called up to train with Barcelona's first team on occasion.
Standing at 1.90m, he is regarded as a modern-style goalkeeper comfortable playing out from the back, a profile that appealed to Atlético Madrileño as they continue rebuilding their squad for the coming Primera Federación campaign.
"With a lot of excitement and happiness to arrive at this great club. I'm really looking forward to getting started. I want to play a lot of minutes and do well to help the team finish as high up as possible," Astralaga said in his first comments as an Atlético player.
The signing continues a busy summer for Atlético Madrileño, who have been steadily reinforcing their squad since the transfer window opened as they look to build a stronger platform for developing talent through the club's pathway to the first team.
Astralaga's move follows a pattern familiar to many young goalkeepers coming through Spain's top academies, using a loan spell in the second tier to gain senior experience before finding a longer-term home.
His time at Granada was not without setbacks, with an ankle injury interrupting his season in November, but he did enough across his 16 appearances to convince Atletico Madrid's coaching staff of his readiness for a more prominent role. With Fernando Torres continuing to shape his squad ahead of the new campaign, Astralaga will now compete for the starting spot as Atlético Madrileño target a strong push in the third tier this season.