As a youth, Tanguay played in the 1992 and 1993 Quebec International Pee-Wee Hockey Tournaments with a minor ice hockey team from Beauce, Quebec. Following a season of midget AAA hockey with the Cap-de-Madeleine Estacades, Tanguay joined the Halifax Mooseheads of the Quebec Major Junior Hockey League (QMJHL) for the 1996–97 season. He played 70 games, scored 27 goals and 68 points and was named to the QMJHL All-Rookie Team. The following season, he improved to 47 goals and 85 points in 51 league games. He was a member of the eighth place Canadian junior team at the 1998 World Junior Hockey Championship, finishing second in team-scoring with three points in seven games.