[2][3] Aitken started his professional career at Greenock Morton, making his debut against Inverness Caledonian Thistle on 1 April 2000.
Aitken remained with Greenock Morton for two seasons making 19 appearances for the club, before signing for Hamilton Academical in June 2003.
Aitken made his debut for Hamilton and scored his first goal on 2 August 2003 against St Johnstone in the Scottish League Challenge Cup.
He played a major part in Ayr's playoff success in the 2008–09 season, scoring three goals against Brechin and captaining the side all the way to the First division.
[11] After being involved with first-team coaching with Stranraer during the 2015–16 season, Aitken was appointed assistant manager to Brian Reid shortly after announcing his retirement.
[12] Not long after this, former Blues assistant Stephen Farrell was named the new manager of Stranraer, taking up the position following on 23 January 2017.
[15] In February 2023, Aitken took over as manager of West of Scotland Football League side Kilwinning Rangers;[16] bringing in Ian Durrant and Owen Archdeacon to form his coaching team.