Gillen joined the Bairns from North Lanarkshire’s Bargeddie Boys’ Club in 1979, making his debut in a Stirlingshire Cup match that season.
Able to play at either left-wing or left-back, his form in Falkirk’s reserve side earned him a call-up to their first team.
Described as being equally comfortable in defence and attack, his breakthrough came in the 1981-82 season, playing 18 games that campaign plus two substitute appearances for manager John Hagart’s side.
Gillen moved on to Stenhousemuir in 1982 and remained there until 1989, being deployed in a more traditional left-back role and playing 194 games, scoring 11 goals, for the Ochilview club.
After leaving the Warriors, he returned to football’s junior ranks and played with Port Glasgow Juniors until he retired from the game.
Away from the football field, he worked as a contracts manager for an electrical firm.