1990s Nadeau entered eight NASCAR
Busch Grand National Series races for T&G Racing in 1995. At that time, the Busch Grand National Series was considered NASCAR's feeder circuit, a proving ground for drivers who wished to step up to the organization's premiere circuit, the
Winston Cup. It is comparable to
Formula One's relationship with
Formula 2/
Formula 3000/
GP2 Series. He originally signed to run fourteen season races. Nadeau moved to
North Carolina that year on the advice of public relations worker Tom Cotter, He often went to
Hendrick Motorsports to receive tips. Nadeau failed to qualify for his first career NASCAR race, which took place at
Richmond International Raceway. Later that year, he finished 21st at
Hickory, 29th at
New Hampshire, 19th at the
Myrtle Beach Speedway, 20th at the
Milwaukee Mile, 31st at
Lucas Oil Raceway, and did not qualify for the races at
North Carolina Speedway or
Homestead-Miami Speedway. He ran only two races in the Busch Series, finishing 39th in both races and did not qualify at
Darlington. In Formula Opel, he drove a partial season, running in thirteen out of seventeen races for six teams and finished sixth overall, the highest for an American driver. After returning from racing in Europe in 1997, Nadeau moved to the Winston Cup Series and signed a five-race contract with
Precision Products Racing to replace
Morgan Shepherd in the No. 1
Pontiac Grand Prix. During the first races, Nadeau was Shepherd's
spotter, and worked on maintaining Shepherd's car before the races. Nadeau also built his own cars for
Automobile Racing Club of America (ARCA) and Busch Series events. Nadeau made all five races, including a ninth place qualification at
New Hampshire International Speedway, but failed to finish higher than thirtieth and was let go at the end of his contract when the team's sponsor expressed no interest in retaining him. In five races, he had zero top-ten finishes and two DNF's, and finished 54th in season points. He also took part in one race in the Busch Series at
Talladega Superspeedway but failed to qualify. He made his first appearance in an
ARCA Bondo/Mar-Hyde Series car and finished fourth and second in the races he entered. Nadeau's performances during the season caught the interest of 1988 Champion
Bill Elliott and quarterback
Dan Marino, and they offered him the chance to become their second driver. he was released from his contract in July. He entered his first and only race in the Craftsman Truck Series at
Phoenix International Speedway finishing 27th. The following year, Nadeau stayed with Melling and clinched his first top-ten finish at Talladega. In the first half of the year, he announced that he would leave Melling after the season ended. Two weeks after securing fifth at
Watkins Glen, he substituted for the injured
Ernie Irvan to drive the No. 36 Pontiac at
MB2 Motorsports for the remainder of the season. In 34 races, he had two Top 10 finishes and finished 34th in season points. In that year, Nadeau won his first NASCAR-sanctioned event in the
Winston West Series at
Las Vegas Motor Speedway.
2000s 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 34 events; Nadeau finished twentieth in the Winston Cup points standings for that season. The following year, Nadeau stayed with Hendrick Motorsports. He nearly clinched victory in the penultimate race of the season at Atlanta, finishing fourth after running out of fuel midway through the final lap. In 36 races, Nadeau achieved ten top-ten finishes, eight DNFs, and an average finish of 21.1. He finished the season seventeenth in points. During 2001, Nadeau took part in the DIRT Motorsports Series with R&C Motorsports, and co-founded the Tom and Jerry Racing Team with Tom Cotter, which fielded USAC Sprint Car Series driver Tony Hunt. Nadeau raced for four teams in 2002. He started the season by competing in eleven events for Hendrick Motorsports. He had his only top-ten finish of the year, taking eighth place at Bristol Motor Speedway. In early May, Nadeau and Hendrick Motorsports agreed to terminate his contract, citing a lack of performance. He was hired by MBV Motorsports to fill in for the injured
Johnny Benson Jr. for three races, while
Joe Nemechek took over Nadeau's former seat at Hendrick Motorsports. Afterward, Nadeau drove for
Petty Enterprises at
Sonoma where he came close to winning his second Winston Cup race, having a five-second lead with three laps to go but finishing 36th after his car suffered a broken rear-end gear on the race's 107th lap. He subsequently drove one race for
Michael Waltrip Racing at
Chicagoland Speedway, finishing 37th after a steering problem. For the rest of the season, Nadeau was hired by Petty Enterprises to drive
Steve Grissom's No. 44 Dodge car, although he injured his ribs and shoulder in a go-kart accident at his home before the
Old Dominion 500. He was advised by team owner
Kyle Petty to rest, and Grissom replaced Nadeau for the rest of the season. He had competed in 28 out of 36 races, with one Top 10 finish at the
Food City 500, seven DNFs, and an average finish of 27.4. Nadeau finished the 2002 season 37th in points. He partnered sports car driver
Anthony Lazzaro with the Rand Racing team in the
Rolex Sports Car Series to finish first in the SRPII (Sports Racing Prototype) class at
Daytona International Speedway, and in the Busch Series, he finished 20th at the fall Charlotte race. Nadeau started the 2003 season as the driver of the MB2/MBV Motorsports No. 01 Pontiac Grand Prix, and quickly had a fourth place finish at Texas. On May 2, 2003, during a practice session at Richmond International Raceway for the
Pontiac Excitement 400, Nadeau was leading the practice session when he suddenly swerved to avoid a slowing car, spun in turn one and hit the wall, driver's side first, at high speed. His car then slowly scraped across the wall for 50 feet before sliding to a complete stop. NASCAR red-flagged the track to cut Nadeau out of his car.
Jason Keller raced for him at the Richmond race,
Mike Skinner,
Mike Wallace, and
Boris Said raced the No. 01 until the fall Martinsville race, Joe Nemechek raced in the No. 01 for the remainder of the season and for the next few years as Nadeau's replacement. ==Post-racing career==