Milla joins Como, coached by Cesc Fàbregas, and will play Champions League football next season following the club's historic campaign.
Getafe, presided over by Ángel Torres, will receive €6 million for the 31-year-old, who leaves behind four seasons in which he made 134 appearances, scoring three goals and providing 20 assists. He was the club's leading assist provider this season and had been mentioned in several conversations around Luis de la Fuente's Spain squads.
Milla joined Getafe from Granada in July 2022 and had attracted interest from several other clubs this summer, including Al-Nassr and Villarreal, before opting for Como's project. His departure also brings an end to a long-standing midfield partnership with Mauro Arambarri, who left the club earlier in the window.
Milla has steadily built his career, rising through Fuenlabrada, Tenerife and Granada before arriving at Getafe. He now makes the jump to Champions League football alongside Fàbregas, who had already tried to sign him during the last winter transfer window.
The midfielder was key for Getafe this season, helping the club to a historic seventh-place finish that secured Conference League qualification. He was as influential off the pitch as on it, regarded as a central figure in the dressing room, and his departure leaves a gap among the squad's leaders.
Milla said goodbye to Getafe in a message posted on social media.
"It's never easy to say goodbye to a place where you've been so happy. Thank you Getafe CF for these four unforgettable years. Thank you to the club, to José Bordalás and his coaching staff, to my team-mates, and to everyone who makes this team great. And above all, thank you to the fans, you always made me feel at home.
"I leave with my heart full, proud of everything we've experienced, with memories that will stay with me forever. Thank you for everything. Together we made history. See you soon, Geta!"
Fàbregas welcomed his new signing.
"Luis is a player with a great understanding of the game," the Como coach said. "He gives us control, quality and experience in midfield, but above all he has the personality and ambition we're looking for."
"He'll help the team in many ways, both with and without the ball, and we're delighted to welcome him to Como," Fàbregas added.