Carles Aleñá has been an FC Barcelona player since the age of eight. His natural ability has seen him rise quickly through the youth teams to reach Barça B. When he was a still officially an U19A player, he was already a fixture in the B squad.

On 30 November 2016 he made his debut for Luis Enrique's first team in the Copa del Rey tie away at Hércules which ended 1-1. The midfielder from Matatró scored Barça's only goal of the game with an excellent effort from outside the box.

On 6 September 2017, Aleñá signed a contract extension with FC Barcelona for the next three seasons with an option for two more should he reach the first team. For the 2018/19 season, Aleñá was confirmed as part of the FC Barcelona first team squad. 

In the 2019/20 winter transfer market, Aleñá left on loan for half a season to Betis, where he played 19 games and scored a goal.