Piquet's father, a physician who later served as Minister for Health in Brazil, pushed him toward tennis and disapproved of motor racing. To conceal his karting activities, the young driver adopted his mother's maiden name Piquet — misspelled as "Piket" — and would eventually make it his permanent identity. He became Brazilian national karting champion in 1971 and 1972 before winning the Formula Vee Brazil championship in 1976.
On the advice of Emerson Fittipaldi, Piquet moved to Europe and immediately made an impression. In the 1978 British Formula Three season he broke Jackie Stewart's all-time record for wins in a single season. That same year he made his Formula One debut for the Ensign team at the German Grand Prix before driving for McLaren and then earning a permanent seat at Brabham.
Piquet's long partnership with Brabham produced two world championships. In 1980 he finished runner-up to Alan Jones, then clinched his first title at the 1981 Caesars Palace Grand Prix in Las Vegas under extreme desert heat — he was so dehydrated and exhausted that he vomited during the race and had to be lifted from the car afterwards. His second championship came in 1983, driving the arrow-shaped Brabham BT52 with a BMW turbocharged engine, making it the first turbocharged car to win the Formula One World Championship and BMW's only title in the sport. A third-place finish at the season-ending South African Grand Prix, while title rival Alain Prost retired, sealed the crown.
The 1982 season was defined by BMW engine unreliability, though Piquet still won in Canada — BMW's maiden Formula One victory. In Germany that year he was leading the race when he collided with Eliseo Salazar and physically attacked the Chilean driver on the side of the track, live on television. In 1984, despite winning in Canada and Detroit, McLaren dominated and Piquet finished fifth in the championship. His sole 1985 win came at the French Grand Prix at Paul Ricard, where the BMW turbo propelled the Brabham to what was then the outright speed record on a Formula One straight — 338 km/h on the Mistral Straight.
A move to Williams alongside Nigel Mansell produced the most turbulent chapter of Piquet's career. The pair's fierce rivalry and mutual antagonism — including a notorious 1988 magazine interview in which Piquet called Mansell "an uneducated blockhead" and insulted his wife — allowed Alain Prost to steal the 1986 championship in an inferior McLaren despite Piquet winning four races that season, more than in any of his championship campaigns.
In 1987 Piquet took his third and final title. A serious qualifying crash at Imola — he later revealed the accident cost him 80% of his depth perception, which he kept secret from the team throughout the season — hampered his ability to lead from the front. He adopted what he called a "percentage driving policy," rarely finishing off the podium from Detroit to Portugal, while Mansell won more races outright. Piquet announced mid-season that he had signed for Lotus, believing Williams had never honored their promise of number-one status.
The Lotus years were a steep decline. The 1988 Lotus 100T shared Honda's V6 turbo engine specification with the dominant McLarens but was aerodynamically compromised and chronically unreliable. Piquet managed only three third-place finishes and no wins. In 1989 the team switched to a Judd V8 with significantly less power, and Piquet and teammate Satoru Nakajima both failed to qualify for the Belgian Grand Prix at Spa.
At Benetton from 1990, driving the Ford-Cosworth HB-powered B190, Piquet recaptured something of his earlier form. He won back-to-back season-closing races in Japan and Australia in 1990 — the Australian win was the 500th World Championship Grand Prix — to finish third in the standings. His final Formula One victory came in Montreal in 1991 when Mansell's Williams-Renault stalled on the last lap while leading.
After retiring from Formula One, Piquet attempted the Indianapolis 500 twice. In 1992 he suffered serious foot and ankle injuries in a practice accident and missed the race. In 1993 he qualified and started 13th but retired after 38 laps with engine failure.
In sportscar racing, Piquet won the 1000 km Nurburgring in 1981 alongside Hans-Joachim Stuck in a BMW M1. He competed at the 24 Hours of Le Mans in 1996 and 1997 in a McLaren F1 GTR, finishing eighth overall in 1996. On 20 January 2006 he won the 50th Mil Milhas Brasileiras at Interlagos in an Aston Martin DBR9, sharing the car with his son Nelson Piquet Jr. and others.
Piquet was inducted into the International Motorsports Hall of Fame in 2000. Two circuits — in Rio de Janeiro (the former Jacarepaguá) and in Brasilia — were named the Autódromo Internacional Nelson Piquet in his honor, though the Rio circuit has since been demolished. Autosport ranked him 13th among the greatest Formula One drivers in 2009; BBC Sport ranked him 16th in 2012.
His post-racing reputation has been significantly damaged by a pattern of derogatory public statements. In 2021 he used a racial slur in reference to Lewis Hamilton when discussing an incident at the 2021 British Grand Prix; the comments resurfaced in 2022 and earned widespread condemnation from the Formula One community. In July 2022 he was banned from the Formula One paddock. In March 2023 a Brazilian court ordered him to pay approximately US$950,000 in moral damages. The ban was lifted by the end of 2024.
During the 2008 Singapore Grand Prix Crashgate scandal, his son Nelson Piquet Jr. revealed he had been ordered by Renault to crash deliberately. Piquet Sr. pledged to use his resources to expose why his son received those instructions, and both were ultimately paid damages in settlement.