Duhamel (pronounced doo-ah-MEL) was born in Minot, North Dakota to Larry David Duhamel (an advertising salesman) and Bonnie (a phys ed teacher); his parents divorced during his youth, and he grew up with his mother and his three sisters, Ashley, Cassidy and McKenzie. Duhamel attended Minot State University, earning a Bachelor of Science degree in Biology and playing on the university's football team, as a quarterback. Although he had wanted to be a dentist from the time he was a sophomore in high school, he was one credit short of eligibility for dental school.

Duhamel then moved to California, where he began working as a model for fashion magazines, winning the IMTA "Model of the Year" award in 1997.

Duhamel's first acting role was in 1999, starring in the independent film The Picture of Dorian Gray as the title character. ABC then called him to test for the soap opera All My Children; ABC executives wanted him for the role so much that they postponed the character's first air date by more than a month to accommodate his schedule. Duhamel played the role between 1999 and 2002; while appearing on the show, it was revealed that he had posed nude for a performance art coffee table book a couple of years before. The book was re-published and sold many more copies.

In 2003, he was cast in the successful television series, Las Vegas. Duhamel gained renown and subsequently starred in the title role of the film, Win a Date with Tad Hamilton! (2004), also starring Kate Bosworth and Topher Grace. The movie performed only moderately at the box office, grossing a little over $16 million [1]; the same year, Duhamel was included in People Magazine's list of "50 most beautiful people in the world".

Duhamel was cast in the adventure film Eight Below (at the time known as Antarctica), but the film was put on hold and Duhamel was replaced by actor Paul Walker. Duhamel will play the lead in Turistas, due out in theatres sometime this year.

In January 2004, Duhamel was engaged to his girlfriend of several years, model Kristy Pierce, although they have since broken off their engagement.

Duhamel, who lives in Brentwood, is currently dating singer Stacy Ferguson (of the Black Eyed Peas), having met her in September 2004, during her guest appearance on his show, Las Vegas; the two have denied rumors of an engagement.

Duhamel has also branched into entrepreneurship, opening a restaurant, 10 North Main, in his hometown. He enjoys basketball, football, skiing and golf.