The 30 year old is moving back to his home country after 3 seasons with Bayer Leverkusen, with whom he won the German double in the 2023/24 season under former manager Xabi Alonso.
A leaves for a reported fee of around €25M and signs a deal until 2030 as he commits to the Spanish side for what may be the remainder of his career.
The Spaniard, who is representing his country at the World Cup, featured 145 times for Die Werkself, scoring 30 goals and providing 45 assists.
Atletico Madrid confirmed the deal on Tuesday afternoon as they welcomed him to the side.
“Atlético de Madrid and Bayer Leverkusen have reached an agreement for the transfer of Alejandro Grimaldo, who has signed for our club until June 30, 2030.
“The Spaniard is versatile left-back who can also play as a wing-back, central midfielder and even an attacking midfielder. He stands out for his technical ability and vision, which allow him to contribute in attack by scoring goals and providing assists.
“Welcome to Atleti, Grimaldo!”
Grimaldo, who won the 2024 European Championship, will be looking to replicate such success at the World Cup where Spain are one of the favourites to go all the way for the first time since 2010.