During the 2012–13 NHL lockout, Rielly was selected to represent Canada at the 2013 IIHF World U20 Championships, again finishing in fourth place. In 2016, Rielly was named to Canada's roster for the 2016 IIHF World Championship, where he was named one of Canada's most valuable players. Canada would go on to win the tournament with a 2–0 victory over Finland in the final. Throughout the tournament, Rielly recorded the most ice time of any player on Canada. For this accomplishment, he was named to the tournament All-Star team.