Duhamel grew up in a motorsport family, with his father Yvon being one of Canada's most celebrated motorcycle racers. He began his professional racing career in 1988, competing for Honda in the FIM Endurance Cup and for Team Suzuki in the Canadian Superbike Championship. His early seasons also included a limited AMA 250 Grand Prix schedule, establishing his versatility across classes and series before he found his greatest success in American domestic competition.
Duhamel won his first AMA Superbike race in 1990 at Heartland Park Topeka and was named the AMA Superbike Rookie of the Year. In 1991, he won the Daytona 200 as a late replacement for the injured Randy Renfrow, and also captured the AMA 600cc SuperSport Championship with seven race victories that season.
The 1992 season saw Duhamel win the FIM World Endurance Team Championship with Team Kawasaki France. He also made his sole appearance in the 500cc Grand Prix World Championship that year, finishing twelfth for Team Yamaha France. In 1993, he claimed a second AMA 600cc SuperSport title on Kawasaki, again with seven wins, and delivered a memorable Superbike victory at Sears Point, beating Doug Polen by a razor-thin margin.
In 1994, Harley-Davidson selected Duhamel to pilot their experimental VR1000 Superbike. Although he led portions of races at Mid-Ohio and Brainerd, these were ultimately the only occasions the Harley VR1000 ever led an AMA Superbike race. The following year proved transformative: in 1995, Duhamel became the first Canadian to win the AMA Superbike Championship and was named AMA Pro Athlete of the Year. During that season he recorded six consecutive AMA Superbike victories, breaking Wayne Rainey's record of five, and won nine of eleven 600 SuperSport events, breaking Doug Polen's record of eight straight victories. He also finished third and fourth at the U.S. round of World Superbike that year.
Duhamel continued dominating the SuperSport category, winning further titles in 1996 and 1997 — his fourth and fifth 600cc SuperSport championships, respectively. In the Superbike class, he won four races in each of those seasons, although the title eluded him both years to Doug Chandler. He also became the all-time winningest rider in AMA SuperSport history during the 1996 season, surpassing the record with his 28th career victory in that class.
A serious crash during qualifying at New Hampshire International Speedway in 1998 ended his season early and left him with lingering injuries heading into 1999. Despite this, he made a dramatic return at Daytona, winning both the AMA Superbike and 600 Supersport races at the season opener, before another injury at Road Atlanta cut his year short again.
Duhamel returned to winning form in 2000 with victories at Brainerd and Road America for Honda and remained competitive in the early 2000s, consistently placing among the leaders in both Superbike and Supersport. His 2003 campaign with American Honda included four Superbike wins and a Supersport victory at Brainerd. In 2004, he won the Daytona 200 — one of the most prestigious events in American motorcycle racing — for the second time in his career, and also claimed the AMA Formula Xtreme Championship.
He defended the Formula Xtreme title in 2005, winning four events and edging Jake Zemke in a closely contested championship battle.
In July 2007, Duhamel made a wildcard appearance for Gresini Honda at the United States Grand Prix at Laguna Seca, substituting for the injured Toni Elías. The gap between his 1992 Grand Prix appearance and this 2007 return represented the longest gap between starts in the top class, a record that still stands. He struggled to adapt to the unfamiliar Honda RC212V and withdrew from the race. Later that year, in August 2007, he suffered a lacerated liver, perforated lung, and bruised lung in a crash during practice at Road Atlanta.
Duhamel returned to AMA Superbike competition in 2008 with the Factory Honda team aboard a CBR1000RR-based Superbike, recording five top-five finishes and finishing seventh in the championship. In 2012, after a three-year hiatus, he won the FIM e-Power and TTXGP electric motorcycle race, demonstrating his competitive instincts remained sharp. In February 2016, he announced he would emerge from retirement once more to race in the Bol d'Or Classic endurance race in France.
Duhamel was inducted into the AMA Motorcycle Hall of Fame in 2016 and the Motorsports Hall of Fame of America in 2025. With 32 AMA Superbike victories, he is tied for fourth on the all-time wins list alongside Toni Elias, behind Mat Mladin (82), Josh Hayes (61), and Cameron Beaubier (38). His five 600cc SuperSport titles remain a defining part of his legacy. As the first Canadian AMA Superbike champion and a rider who bridged domestic dominance with world-class appearances across endurance, Grand Prix, and electric racing, Duhamel stands as one of the most versatile and accomplished North American motorcycle racers of his generation.