 He then joined the AFC Wimbledon Senior Academy at South Thames College, where he got picked for the England Colleges team.The midfielder made his league debut for "The Dons" in a Conference game against Crawley Town in a 3–1 defeat on 18 March 2011, coming on as a substitute for Luke Moore.Kiernan only featured in one more game in the 2010–11 season, a 0–0 draw with Forest Green Rovers, which was his first League start for the club, securing a place in the Conference play-offs.