 He was spotted by a Leeds United scout while playing for his local junior team, Rutherglen Glencairn, and joined the West Yorkshire club in June 1947, aged 24.He made his debut in November 1947, and in the following season made the right back position his own, staying in the team for the next ten seasons.Dunn was a key player for both manager Frank Buckley and his successor, Raich Carter; the defensive line of Dunn, Grenville Hair, Eric Kerfoot and Jack Charlton was a key component in Leeds' promotion to Division One in 1955–56.