Born in
Salford,
Greater Manchester, Tierney signed for
Manchester United as a trainee in July 1999 and as a professional 12 months later. He was loaned out to
Crewe Alexandra (where he scored his first career goal against Blackpool),
Colchester United, and
Bradford City. He made his senior debut for Manchester United on 3 December 2003 against
West Bromwich Albion in the
League Cup. He signed for Livingston on 16 June 2005 having been released by Manchester United, but failed to impress in his first season at the club and they were relegated from the
Scottish Premier League. He joined
Blackpool on 2 June 2006 on a
free transfer. In July 2007, Blackpool manager
Simon Grayson allowed Tierney to join
Stockport County in a six-month loan deal. At Stockport he scored once against
Macclesfield in the
Football League Trophy. Tierney returned to Blackpool in January 2008, and in May 2008, he was released by the club. In September 2008 he signed for
Conference National club
Altrincham. However, he left the club after less than a month. ==International career==