Monk competed in his first Commonwealth Games in 2006, after being asked to fill in for Ian Thorpe. He finished seventh in the 100m freestyle event, and ninth in the 200m. As a member of the Australian men's relay team, he won gold in the 4×100-metre medley (as a heat swimmer) and bronze in the 4×200-metre freestyle. Later that year he competed in the 2006 Pan Pacific Swimming Championships, finishing sixth in the 200-metre freestyle, and taking the bronze medal in the men's 4×100-metre and 4×200-metre freestyle relay events.