Career
He previously played for and in the League of Ireland prior to joining in January 2007. He has represented the Republic of Ireland at under-16, under-21 and B international level Club In January 2007, Dillon moved to Scottish side for an undisclosed fee.
In March 2008 he collected a Scottish League Cup runners-up medal despite being an unused substitute in the final.
However, on 15 May 2010, he was then a part of the team who defeated Ross County 3–0 to lift the Scottish Cup at Hampden Park. Not long after the beginning of the 2012-2013 season Dillon signed a contract extension that would keep him at the club until May 2015.
He was then appointed club captain by manager Jackie McNamara for the 2013-2014 season. International Dillon represented the Republic of Ireland Under-16 team at the 2000 Union of European Football Associations European Under-16 Football Championship and is a former Republic of Ireland under-21 international who represented his country at the 2003 Fédération internationale de football association World Youth Championship, appearing as a substitute in the second round exit.
Dillon also represented the Republic of Ireland under-21 team on one occasion and played alongside United teammate Noel Hunt for the Ireland B team in October 2007 in a match against Scotland who included team mate Darren Dods.