Jean-Sebastien Giguere starred with Laval Laurentide Lanaudiere of the Quebec Midget AAA Hockey League and then with the Verdun College Francais and Halifax Mooseheads of the QMJHL. Selected 13th overall by the Hartford Whalers in 1995 NHL Entry Draft, Giguere saw brief action in the NHL before he was returned for one more year of junior hockey.
In August, 1997 Giguere was traded to the Calgary Flames and formed a fine goaltending partnership in Sait John of the AHL with Tyler Moss. Following the 1997-98 season the two shared the Hap Holmes Memorial trophy for allowing the fewest goals in the league. Giguere showed promise during a couple of recalls to the NHL but was overshadowed by the unexpected development of Fred Brathwaite in the Flames' goal. Giguere was dealt to Anaheim prior to the 2000-01 season and ended up supplanting Dominic Roussel as Guy Hebert's back up.
Giguere would split his first season in Anaheim with the Ducks and their AHL affiliate in Cincinnati before earning the outright number one position the following year and guiding Anaheim to the post-season in 2003.
In his first playoff game, Giguere and his Mighty Duck teammates defeated the defending Stanley Cup champion Detroit Red Wings 2-1 in triple overtime. Giguere stopped an astounding 63 shots in the contest, breaking Jiri Chra's NHL record of most saves in a playoff debut by two. Giguere continued his playoff OT shutout streak to a record 168:27 and counting. In so doing, he led his Ducks to the Stanley Cup Final, only to lose to the New Jersey Devils in a hard fought seven game series. Giguere earned playoff MVP honours, winning the Conn Smythe Trophy, thus becoming the fifth player to ever win the award from a losing team.
Coming off a playoff MVP performance in 2002-03, Giguere and the Ducks struggled in 2003-04. Despite the off-season acquisitions of Sergei Fedorov and Vaclav Prospal, the club missed the playoffs after being Stanley Cup finalists the previous year.
After the NHL lockout, Giguere returned to the Ducks crease and posted a stellar 30-win season. However, the club was ousted in the playoffs that season by the eventual Western Conference champion Edmonton Oilers. In 2006-07, the newly named "Anaheim Ducks" returned with a vengeance. Giguere finished the season with a record of 36-10-8 as the club set new franchise records in wins (48) and points (110). The Ducks momentum carried through to the 2007 NHL playoffs as the club steamrolled through the league with a 16-5 record en rout to the Stanley Cup.
On the international stage, Giguere has represented his homeland at the 2001 World Championships and helped them capture gold in 2004.
On January 31, 2010, Giguere's time in Anaheim would come to an end. He was traded to Toronto in exchange for goaltender Vesa Toskala and forward Jason Blake.
Giguere's time in Toronto would be riddled with injury. He was limited to just 33 games in 2010-11 due to groin injuries and the veteran goaltender found himself a free agent at season's end. On July 1, 2011, Giguere signed on with the Colorado Avalanche.