A former Bendigo Pioneers captain and best and fairest winner, Gallagher joined the Western Bulldogs at pick 39 in the 2022 draft. He debuted against Melbourne in round 1, 2024 and played 20 games that season, before injury restricted the 181cm midfielder to 5 senior appearances in 2025. Delisted by the Bulldogs at the end of the 2026 season, he has played 28 AFL games and kicked 10 goals.