Gormley participated in the Canadian national junior team's selection camp for the 2010 World Junior Ice Hockey Championships, but failed to make the under-20 team as a 17-year-old. He was expected to participate in the 2011 tournament, but was sidelined with a knee injury. The following year, he was selected to the team for the 2012 World Juniors, held in Alberta. During the preliminary round, he was named Canada's player of the game after scoring two goals and an assist in a 10–2 win against Denmark. He was named the top defenseman of the tournament in addition to being named to the tournament All-Star team.