Opoku's career began in Ghana with Division One club Okyeman Planners.[3] He scored eleven goals in his final season, 2016, with Okyeman.[3] In February 2017, Opoku joined Premier League team Middlesbrough on a long-term contract.[4][5] He was immediately loaned out to Levadia Tallinn of the Meistriliiga for eighteen months.[4][5] He made his Levadia debut on 3 March in the league versus Flora.[1] During his time in Estonia, Opoku mainly featured for their reserve team in the Esiliiga.[1] In total, he scored seven goals in fifteen games in the tier two.[1] His loan with Levadia was terminated in June 2017.[6]