Luongo made his international debut at the 1995 World U-17 Hockey Challenge in Moncton, New Brunswick, with Team Québec, winning bronze. Three years later, he was named to the Canadian national junior team for the 1998 World Junior Championships in Finland. He played backup to Victoriaville Tigres goaltender Mathieu Garon, going winless in three appearances with a 3.70 GAA, as Canada finished in eighth place. Luongo became the starting goaltender the following year at the 1999 World Junior Championships in Winnipeg, Manitoba, appearing in seven of Canada's eight games. He recorded a shutout in the first game of the tournament against the Czech Republic, making 36 saves in a 0–0 tie. He went on to help Team Canada to the gold medal game against Russia, but lost in overtime, surrendering a goal to Artem Chubarov. With a 1.92 GAA and two shutouts, Luongo was given Best Goaltender and All-Star Team honours.