 He made his managerial bow at Finn Park on 4 September.He guided the club to third place in the First Division table in 2005, their highest league placing since 1999, and fourth place the following season before delivering the club their first ever piece of silverware when he guided Cobh Ramblers to the First Division title in 2007.Cobh were relegated in 2008 from the Premier Division and Henderson took up the manager's post at Waterford United in December 2008.