Pau Cubarsí arrived at La Masia from Girona on 1 July 2018 as a U12 player. The 2023/24 season was a key moment in his career as he made his competitive debut with the first team.

A centre back who provides leadership and decisiveness in defence, while also being able to bring the ball out, as an U18 player during the 2023/24 season, he played for Barça Atlètic, while receiving squad call ups and playing time with the first team. Salamanca will always remain a fond memory for Pau Cubarsí, as the 16-year-old centre back made his competitive debut for the Club in January 2024 against Unionistas in the Copa del Rey. A month earlier he had already featured for the first team in a friendly game in Dallas against Club América.

In the 2024/25 campaign with Hansi Flick as coach, the centre back continued to be a fixture in the starting XI. Cubarsí made 56 appearances over a season in which he claimed his first honours as a blaugrana, winning the Spanish Super Cup, the Copa del Rey and the league. The defender scored his first goal for the club in the Copa del Rey tie against Atlético Madrid and he also extended his contract with FC Barcelona until 2029. 

The centre back played in 24 first team official fixtures in the 2023/24 season as well as playing in the U17 World Cup in the 2023/24 season and making his debut for the full Spanish national side. In the summer of 2024 he claimed a goal medal playing for Spain in the Paris Olympics.