Nadeau was born on September 9, 1970, and grew up in Danbury, Connecticut. His parents were Gerald Joseph, a roofer, and veteran in the United States Army (1944–2007) and Pauline Cyr Nadeau. Nadeau’s ancestors originate from St. John’s Valley, Maine. He has one sister, Debbie. Nadeau was educated at Henry Abbott Technical High School and studied automotive technology. His family had connections to auto racing; Gerald raced modifieds at the Danbury Race Arena. Nadeau was given a go-kart by his father when he was four and one-half years old. He also worked with his father in the construction industry to support his career. Speaking about his father’s role in his career, Nadeau said, “I learned a lot from my dad, Gerry, while I was growing up. He wasn’t afraid to yell and get on my toes to do my job because he hated to lose and I hated to lose. He made me the hungriest guy on the race track.”

At age seven, he came first in the eight- to twelve-year-old karting championship held in Bethany, Connecticut. In 1988, aged eighteen, Nadeau won his first World Karting Association (WKA) Gold Cup championship. Motorsports Talent Scout, Dicken Wear, had seen Jerry Race for a number of years in Karting and asked if he would like to drive his SCCA SS/C Toyota Celica at an EMRA open track event at Lime Rock Park. Jerry caught the eye of Skip Barber and a few other driving instructors that day. Afterward, he was introduced to Bruce MacInnes and fellow graduates Walter Bladstrom, Tom Cotter, Bill Fisher, Bob Kullas, Frank Martinelli, and Art Regan who gave Nadeau financial support. He defended his karting title for the next two years. In 1991, he took the WKA Grand National Championship. In the same year, Nadeau moved into car racing, driving in the Skip Barber Eastern Series. He took eight victories and became the Rookie of the Year. At the end of 1991, Nadeau won the $100,000 Barber Pro Series shoot-out, allowing him to race in the Barber Dodge Pro Series.

Nadeau drove alongside sports car driver Gene Felton for the Jill Prewitt team which entered the 1992 12 Hours of Sebring, but retired after forty-eight laps because of a differential problem. He also took part in karting events in St. Petersburg, Russia, competing on an ice track, winning two out of eight races. Nadeau later stated the experience helped him to develop the skill of not using his car’s brakes on slippery surfaces. In 1993, he raced in the Barber Pro Series, where he finished with one win and took fifth in the points standings. Nadeau also drove in the European Formula Ford Festival winning the qualifying race and coming second in the semi-finals behind Formula Ford champion Peter Duke. Nadeau secured fourth in the final heat. He also took five, top-four finishes in the Firestone Firehawk Series. Nadeau improved in the Barber Pro Series in 1994 by finishing fifth in the championship with two victories. In 1995, he took two victories but fell to thirteenth overall in the standings.

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, and was on a budget of $200. 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 twenty-first at Hickory, twenty-ninth at New Hampshire, nineteenth at the Myrtle Beach Speedway, twentieth at the Milwaukee Mile, thirty-first at Lucas Oil Raceway, and did not qualify for the races at North Carolina Speedway or Homestead-Miami Speedway.

The following year, Nadeau moved to M.P.H. Racing and planned to run ten races in the Busch Series in 1996, in combination with a full season in the Formula Opel European Union Series Championship. He ran only two races in the Busch Series, finishing thirty-ninth 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. He later declined a move into the Formula 3000 series, opting for a return to NASCAR. In November 1996, Nadeau and Barber Dodge Pro Series driver Tony Renna represented the United States in the EDFA Nations Cup held at Donington Park and won the silver medal, finishing behind Germany.

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 no Top Ten finishes, two Did Not Finishes (DNF) and finished fifty-fourth 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.

Nadeau started his rookie season in 1998 with Elliott-Marino Racing driving the No. 13 Ford car, owned by Marino. After sixteen races, and missing one race due to food poisoning, he was released from his contract in July. One week later, he was signed to Melling Racing to drive the No. 9 car. Melling and Nadeau used the second half of the season to develop a consistent program in preparation for the 1999 season. He had no top 10 finishes, seven DNF’s, an average finish of 24.2, and had two results in the top 20. Nadeau finished 36th in the Winston Cup points standings for that season and was third in the NASCAR Rookie of the Year Award standings. He entered his first and only race in the Craftsman Truck Series at Phoenix International Speedway finishing twenty-seventh.

On December 11, 1999, Nadeau married long-time girlfriend Jada Blanchard in the Bahamas. Together, they have a daughter, Natalie Kate (born February 17, 2003). One year after Nadeau suffered his accident, the couple divorced. In 2012, Nadeau remarried to Maryana, a Ukrainian. He has a daughter from that relationship.

For the 2000 season, Nadeau was hired by Hendrick Motorsports to drive the No. 25 Chevrolet car, 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.

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, finishing thirty-sixth 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.

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. After he hit the wall, Nadeau responded to his crew before falling unconscious. NASCAR red-flagged the track to cut Nadeau out of his car. He was airlifted to a local hospital in critical condition, only given a six percent chance of surviving his injuries. Nadeau suffered complete immobility of the left side of his body, a skull fracture, concussion, a collapsed lung, and several broken ribs. The injuries meant he required a medical ventilator to breathe. Jason Keller raced for him at the Richmond race, Mike Skinner, Mike Wallace, and Boris Said raced the 01 until the fall Martinsville Race, Joe Nemechek raced in the 01 for the remainder of the season and for the next few years as Nadeau’s replacement.

In fall 2003, Nadeau began discussions with MB2 Motorsports boss Jay Frye about a long-term comeback. Frye gave Nadeau a test at Concord Speedway, where he was unable to feel his car’s brake pedal. He also suffered a loss of stamina during this test. Because of the effects of his accident, Nadeau had to learn to walk. He also experienced slurred speech. He undertook physical therapy five times during the week. This was later reduced to three when his condition improved. While Nadeau received a small financial settlement from NASCAR, it was not enough to pay for all of his rehabilitation, so he sold his large house near Lake Norman and moved to Davidson, North Carolina. He also suffered from depression caused by the loss of his racing career.

MB2 Motorsports entered into a partnership to create a recovery driving program for Nadeau which included competing in the Nextel Cup, the Busch Series and ARCA events in 2004. During that year, Nadeau served as a karting instructor at the Lime Rock Park and returned to NASCAR as a spotter for Busch Series driver Todd Szegedy. He worked with the Clay Andrews Racing Busch Series team as a mentor for rookie David Gilliland in 2006, who went on to win the Meijer 300 and earned a ride with Robert Yates Racing later that season. He raced in the Old School Racing Champion’s Tour in 2008. In 2011, Nadeau became a mentor to Truck Series rookie Jeffrey Earnhardt, son of Kerry and grandson of Dale. In 2012, Nadeau began involvement with the B.R.A.K.E.S. program in Lake Norman, North Carolina, which teaches children how to drive. In September 2013, he received a sports award from the Danbury Old Timers.

In a 2016 interview with Autoweek, Nadeau was candid about his life after the crash: