The following year Stewart was selected to play for Canada in the 2004 World Junior Ice Hockey Championships in Helsinki and Hämeenlinna, Finland. Canada went unbeaten in the preliminary round and advanced to the final of the elimination round, where they faced the United States team. During the second period of the final, Stewart scored a goal to put Canada ahead 3–1. It was his third point of the game, as he had made assists in the two previous goals. However, Canada conceded three goals in the third period, losing 4–3 and receiving the silver medal. Stewart finished the tournament with 11 points, tying teammate Nigel Dawes and US player Zach Parise for the tournament lead in points scored. Having scored one more goal than Stewart and Parise, Dawes was officially named the tournament's leading scorer. Later in the year Stewart was selected to play in the 2004 ADT Canada-Russia Challenge as part of the OHL All-Stars team, and later he was named an alternate captain. He scored a short handed goal in the OHL's second game of the series, a 5–2 win. The OHL won both of its games in the series, helping the CHL to a 4–2 win in the series.