Barr played for Falkirk, Heart of Midlothian, Forfar Athletic, Kilmarnock, Ross County, Dumbarton, Greenock Morton and Stirling Albion, mainly as a defender.

[2] Barr went on to sign for Falkirk on 12 July 2002,[3] and after suffering a first anterior cruciate ligament injury during his apprenticeship,[1] he made his first team debut on 13 March 2004, as a substitute against Queen of the South.

[21] On 25 January 2010, it was announced that Barr had signed a 3-year pre-contract with Heart of Midlothian, and would complete his move to Edinburgh upon the expiration of his contract with Falkirk at the end of the season.

[1] In the 2012 Scottish Cup Final, Barr started the match in central midfield and scored the opening goal in a 5–1 win against Hibernian.

[34] He scored his first goal for the club in a league match against Inverness Caledonian Thistle,[35] and his second followed in a Scottish Cup defeat to Dundee United.

[36] The cup loss to Dundee United proved to be his final game for the club as he was ruled out for several months with a hip injury shortly afterwards.

[39] After leaving Kilmarnock, Barr went on trial with Scottish Premiership side Partick Thistle in July 2014[39] and also played as a trialist in pre-season for Motherwell.

[47] He extended his deal in January 2016, rejecting a full-time offer from a rival club, after making 22 appearances during the first half of the season, scoring twice.

[50] Barr rejected a new deal from Dumbarton in the summer of 2017 and joined fellow Championship side Greenock Morton as the club's development team head coach, whilst still being registered as a player.

[59] He retained his place and was named in George Burley's squad for Scotland's World Cup qualifying matches against Macedonia and Iceland.