Andretti also raced alongside his father in the Riverside 6 Hours where they were joined by A. J. Foyt and Preston Henn, but the Porsche 935 failed to finish.

The father and son duo paired up again the 1984 24 Hours of Daytona, this time in a full-works Porsche 962, which made its race debut.

They were competitive in the first half of the race until the Andretti family's car needed minor repairs before lapsing on to five cylinders, finishing sixth overall.

He won two races that season, Molson Indy Toronto and the 1989 Marlboro 500 at the Michigan International Speedway, placing third in points.

In the second-to-last race of the season at Nazareth, Unser crashed out, giving Andretti a huge opportunity to close the gap.

Andretti's season started slowly, recording DNFs in the opening two events, then the heartbreaking second place at the Indy 500.

Despite taking two more wins later in the year, including the season finale at Laguna Seca, Rahal beat him again to the title by just four points.

In 1991, he led with 12 laps remaining, but finished second to Rick Mears after battling the multiple Indy 500 winner.

[21] For the 1993 season, Andretti signed for Marlboro McLaren to partner with the triple World Drivers' Champion Ayrton Senna in their Ford HBD V8-powered MP4/8.

The rule changes introduced that season destroyed his hopes of unrestricted laps in free practice during which he could learn the tracks, as most were unfamiliar to him.

He then qualified sixth for the Sega European Grand Prix at Donington Park but collided with Karl Wendlinger's Sauber on the opening lap.

Next time out at Imola, he again fell foul of Wendlinger after a drive that might have ended with a visit to the podium, and many critics cited this as the key turning point for the American.

[23][24] In the 1993 Spanish Grand Prix, Andretti finally completed a race, finishing fifth amongst the established front runners.

[24] His showing was criticized by former McLaren World Champion James Hunt because Andretti was lapped by his teammate Senna.

Highly technical aspects which he was not used to in the technologically simpler Indy cars such as active suspension and traction control hampered Andretti's chances as did the standing starts used in F1.

also felt that since he commuted to races and test sessions from the United States, rather than relocating full-time to Europe, this was also a contributing factor to his lack of success in Formula One.

Throughout the season, Senna experienced similar reliability problems to Andretti, mainly electronic gremlins, particularly in San Marino, Canada, Hungary, and Belgium, although Häkkinen equalled Andretti's third place Monza finish in Japan, while Senna won both the Japanese Grand Prix and the season ending Australian Grand Prix, his final race for McLaren.

Häkkinen had also said that Andretti's mental approach was wrong, and he did not realize the kind of sacrifices one needed to make in order to succeed in Formula One.

He went on to win in his very first race back in the series at the 1994 Australian FAI Indycar Grand Prix, around the Surfers Paradise Street Circuit in Queensland, Australia, having led every lap along the way.

In 2000 the team used Lola chassis and Andretti won the Firestone Firehawk 300 held at Twin Ring Motegi in Japan, and again in Toronto.

[35] For 2001, Andretti made the decision to move to Team Green as he wanted to try to win the Indianapolis 500 and Newman/Haas refused to enter the Indy Racing League event.

A punctured tyre, and a minor collision in the pits with eventual winner Hélio Castroneves, driving for car owner Roger Penske, slowed him down, and at the end of the day, Andretti settled for 3rd place.

In July, it was announced that he had bought the team and intended to shift the entire operation (which was renamed Andretti Green Racing) to the IRL.

Throughout his time in IndyCar, he retained a consistent and impressive record, finishing in the top ten of the championship on 17 occasions.

[22] Andretti entered in the first four IRL events in 2003, culminating with the 2003 Indianapolis 500, after which he retired from full-time IndyCar racing.

[34][37] The team claimed consecutive IndyCar Series titles in 2004 and 2005, with Tony Kanaan and Dan Wheldon respectively, winning 11 of the 17 races, including the Indianapolis 500.

[38] Andretti returned to the driver's seat for the 2006 Indianapolis 500 in a one-time effort to assist the development of his son, Marco, an IndyCar rookie for the 2006 season.

Andretti leaves driving competition at Indy with a frustrating distinction: the driver who led the most laps (431) without winning the race.

Formula One announced on January 31, 2024, that it had rejected Andretti's latest bid to join the sport by 2026, but that it was leaving the door open for an admission from 2028.

The company also promoted the Indy Grand Prix of Louisiana, the Miami ePrix and the Global RallyCross Championship events at Washington and New York.