He was a corner forward and has played at senior level for the Mayo county team, Connacht provincial team in the Railway Cup and club football for Shrule-Glencorrib in Mayo and later with Dublin club Parnells. He has also played college football for DCU and UUJ. Mortimer has twice played in All-Ireland senior finals (2004 and 2006), losing both. He left the Mayo team in 2012, missing what would have been a third losing All-Ireland senior final appearance. He is famous for his blonde locks.