Liverpudlian Dillon started his career with Crewe Alexandra, however, due to limited opportunities he chose to join Sligo Rovers of the Irish Republic. Here, John excelled and picked up an FAI Cup winner's medal.

The following season, he was a key member of the squad which finished runners up and added a second FAI Cup medal to his honours list. Dillon made over 70 first team appearnaces at Sligo before joining Dundalk.

John spent the second half of the 2013/14 season with Southport in the Football Conference, and joined The Nomads in July 2014 following a successful trial period with the club.

In the 2014-15 season, Dillon made 15(+1) appearances for The Nomads before departing the Club in May 2015.