Having previously only signed a youth agreement with Maastricht, Mbuyamba turned down a three-year professional contract offer from the club in 2019 in favour of a move to La Liga side Barcelona. The move came about following an approach from Barça's academy director and former Netherlands international Patrick Kluivert, and saw him become the fourth Dutch player to join the Catalan side ahead of the 2019–20 season following the club's earlier acquisitions of Frenkie de Jong, Ludovit Reis and Mike van Beijnen. Mbuyamba initially teamed up with the club's under-19 team where he played as both a right-back and centre-back throughout the season, representing the side in the UEFA Youth League, before earning the chance to train with the first team and feature in the match day squad during Barcelona B's 2–0 win against Ejea in January 2020.