He captained the Fulham U23's at the end of the 2018–19 season.[3]
On 2 September 2019, Opoku was sent on loan to League One side Accrington Stanley in order to gain first team experience.[4] He made his Accrington debut against Bristol Rovers on 7 September 2019 in an eventual 3–3 draw. After a 3–1 defeat to Sunderland, in an interview he claimed he would play anywhere the coach put him.[5]
On 24 June 2022, Opoku joined Portuguese Primeira Liga side Arouca on a free transfer, signing a three-year contract.[8][9]
On 14 September 2023, Opoku signed a one-year contract extension with Arouca, until 2026,[10] and was immediately sent on a season-long loan to Süper Lig side İstanbul Başakşehir.[11]