O'Brien began his footballing career at Dunfermline Athletic's Academy, but moved to Cowdenbeath in 2003.
He signed professional terms in 2007, and after loan spells with Rosyth and Kelty Hearts,[1] he made his first team debut on 7 August 2010, in a 2–0 home loss against Ross County.
[2] O'Brien scored his first professional goal on 1 October 2011, in a 1–1 away draw against Arbroath.
[3] At the end of the 2014–15 season, O'Brien signed a two-year contract with Scottish League One side Forfar Athletic.
[5] O'Brien subsequently signed a two-year deal with Angus rivals Arbroath on 1 June 2017.