Barnett was already active in the youth academy of Luton Town, before joining the senior squad of the club in the summer of 2002. After he occasionally came there in the early days to inserts that club managers decided it to the amateur club Aylesbury United borrow. After his return to the 2005/06 season Barnett showed an increase in performance and played himself into the starting lineup of Luton. These services rewarded the fans by the defenders 2006/ 07 elected the best player of the team. Other clubs were at this time aware of him and so he joined in the summer of 2007 to West Bromwich Albion, where Barnett a four -year contract signed. At the end of the season they reached the first place in the Football League Championship and thus promotion to the Premier League, a year later, however, was followed by the immediate re- descent into the second division.
Since 1 January 2011, Leon Barnett plays for Norwich City in the Football League Championship.
- Winning the Football League Championship with West Bromwich Albion: 2008