John Dunn began his playing days with home town club, Eccles Borough. He was signed for Leeds City in the summer of 1913 by celebrated manager Herbert Chapman, when he and another full-back signing, Albert Urwin, were described by the Leeds Mercury as 'players with fine physique. They are a reliable pair of backs who kick with plenty of power'.

Dunn failed to make it into the City first-team and left the club in June 1914 to play for Luton Town.

He returned to Elland Road for a spell during the First World War and played right-back at Elland Road against Sheffield United on 27 December 1915 in place of Charlie Copeland; City lost 3-2.

That was Dunn's only appearance for Leeds and he joined The Wednesday in 1920, playing eight games for them before retiring from senior football in 1921.