Alejandro Grimaldo García was born in Valencia and formed at FC Barcelona, joining La Masia in 2008 and progressing through the youth ranks to Barcelona B, for whom he made more than 80 appearances in the Segunda División without breaking into the first team.

Benfica signed him in January 2016. He established himself as the club's first-choice left back and remained so for seven and a half seasons, passing 250 competitive appearances and winning three Primeira Liga titles, two Taças de Portugal, a Taça da Liga and three Supertaças. His delivery from wide areas and set-piece work made him one of the most productive full backs in Portuguese football.

The 2022/23 campaign was his last and among his best. A first-team fixture under Roger Schmidt, he contributed heavily to the title-winning side and to the run to the Champions League quarter-finals. With his contract expiring, Benfica were unable to agree an extension and he left on a free transfer at the end of June 2023, joining Bayer Leverkusen.