Since retirement, Kennedy has served as a scout, first-team coach and assistant manager to Neil Lennon, Ronny Deila, Brendan Rodgers and Ange Postecoglou.

[3] Kennedy came through Celtic's youth system and signed his first professional contract on the same day as fellow defender Stephen McManus.

[10] Kennedy received high praise for his performance in a 0–0 draw with Barcelona in a UEFA Cup last-16 clash at the Camp Nou in March 2004.

[14] Following his injury, the SFA compensated Celtic with respect to Kennedy's wages, as it had been suffered while he was playing in an international match.

[4][15] Before his injury, Kennedy made enough appearances to qualify for a title medal and played twice in the Scottish Cup win that season.

[16] Kennedy finally resumed training in late 2006, and was an unused substitute for Celtic's Champions League match against A.C. Milan on 20 February 2007.

[18] Kennedy made further appearances for Celtic over the next several months, but during a Champions League match against Shakhtar Donetsk on 28 November 2007, he was stretchered off after he twisted his knee on landing from an aerial challenge.

[25] Kennedy's performances for Norwich were impressive,[26] and he scored in games with Derby County[27] and Preston North End.

[37] Following fine performances for Celtic, Kennedy was called up to the Scotland squad for a friendly against Romania on 31 March 2004, and was selected to start the match.

[38] After 14 minutes, Kennedy sustained a serious injury to his leg after a late challenge by Ionel Ganea,[39] which eventually ruled him out of action for almost three years.

The match was played on 9 August 2011 with Celtic winning 5–2, and the proceeds were donated to Oxfam's East Africa charity appeal.