Semenyo was born and raised in London, though was met with rejection by several clubs in the capital growing up. He was rejected by all of Arsenal, Crystal Palace, Millwall and Tottenham following trials. He joined Bristol City in 2018 at the age of 18 and was sent on loan to non-league side Bath City shortly afterwards. Loans with Newport County and Sunderland, then a League One side, followed.
During the 2020-21 season behind closed doors, Semenyo became a regular for Bristol City, playing 50 times in all competitions. He then developed into one of the Championship's most dynamic forwards across the next couple of years and secured a £10m ($13.5m) move to Bournemouth in the Premier League in January 2023.
Semenyo scored only once in 11 Premier League games to see out the 2022-23 season, but found his feet the following year when Iraola replaced Gary O'Neil as head coach. He grabbed eight goals in 33 matches in 2023-24 and then 11 in 37 matches last term. So far this season, Semenyo has nine goals in 19 Premier League appearances, with only City's Erling Haaland (19) and Brentford's Igor Thiago (14) registering more to date.