He started full-time racing in 1998 and came third in that year's NASCAR Rookie of the Year award standings. After Nadeau took his first Top Ten finish at Talladega Superspeedway in 1999, he won his first NASCAR sanctioned race in the Winston West Series at Las Vegas Motor Speedway. He earned his first Winston Cup victory at Atlanta Motor Speedway the following year. Nadeau achieved his top NASCAR season in 2001 when he finished seventeenth in points, but his racing career ended in 2003 after he suffered serious injuries in a practice crash. He attempted a comeback before moving on to mentor drivers.