St Mirren Born in
Glasgow, Magennis attended
Paisley Grammar School. Magennis joined
St Mirren's youth academy at the age of five He continued to appear for the club throughout the season, scoring his first goal for the club in a narrow win over
Queen of the South. Having impressed manager
Jack Ross with his performances, he was offered a new contract with St Mirren in December 2016 which extended his contract with the club until summer 2019. Now established as a first team player in the
Saints squad, Magennis signed a new contract committing him to the club until the summer of 2020, and after clinching the
2017–18 Scottish Championship title, he further extended his contract with St Mirren to 2021. He was in the side which secured their status in the
Scottish Premiership via the relegation playoff in May 2019. Magennis and Saints suffered a major blow in January 2020, when he injured his knee during a 1–0 defeat to
Rangers, ending his season after having appeared in every match of the campaign until suffering the injury. In September 2020, St Mirren stated they had rejected a "substantial" offer for Magennis from Hibernian. A few days later another offer from the same club was accepted.
Hibernian Magennis signed a five-year deal with
Hibernian on 5 October 2020. On 1 August 2021, Magennis scored
Hibernian's opening
Scottish Premiership goal for the
2021–22 season against
Motherwell which ended in a 3–2 victory for
Hibs. Magennis had a good start to the 2021–22 season, but then missed most of it due to groin and knee injuries. After he suffered from more injury problems during the 2022–23 season, Magennis was allowed to leave Hibs in June 2023. Magennis signed a new one-year contract with Kilmarnock in July 2025. == International career ==