For the 2000 season, Nadeau was hired by Hendrick Motorsports to drive the No. 25 Chevrolet, replacing Wally Dallenbach, Jr. That year, Nadeau won his first NASCAR Winston Cup race in the season's final race at Atlanta Motor Speedway after passing Ward Burton seven laps from the end. Nadeau led 155 laps and won by 1.3 seconds. He became the first driver from Connecticut to win in the series. He finished the 2000 season with five Top Ten finishes, nine DNF's, and an average finish of 23.1 in thirty-four events; Nadeau finished twentieth in the Winston Cup points standings for that season.