Cammalleri made his international debut in 2000, joining the Canadian junior team at the 2001 World Junior Ice Hockey Championships. He had four goals and six points in seven games for Canada, who won the bronze medal. He returned the following year, leading Canada to a silver medal. Cammalleri led the 2002 tournament in scoring with 7 goals and 11 points, and was named the tournament's top forward. He made his debut with the senior team at the 2006 World Championships where he scored one goal and five points in eight games for the fourth place Canadians. He returned for the 2007 tournament held in Moscow, where his seven points helped Canada win the gold medal with a perfect 9–0 record.