Forson was born in Hammersmith, London to parents of Ghanaian origin. The attacking midfielder, who can play out wide as well, started his journey in West Ham United's academy before moving to Tottenham, but couldn't see a clear pathway to break through at the north London club, and ended up joining Manchester United's youth system in 2019.
Ahead of the 2023-24 season, Erik ten Hag included the teenager in his senior squad for United's pre-season tour. On February 2, 2024, Forson was handed his debut as he came on as a substitute in the Red Devils' dramatic 4-3 win over Wolves, and marked the occasion by providing the assist for Kobbie Mainoo's winning goal. After spending the last three games on United's bench, Forson was handed his first start against Fulham on Saturday.