Jani began karting in 1998 and moved to Formula Renault 2000 Eurocup in 2001, competing in both the Eurocup and Italian Formula Renault. In 2003, he joined the Formula Renault V6 Eurocup with Jenzer Motorsport, finishing second in the championship by only four points. The following year, driving for DAMS, he finished fourth.
In 2005, Jani entered the GP2 Series with Racing Engineering, winning two races — at the Hungaroring and at Monza. In 2006, he stood in for Nicolas Lapierre at Arden at Silverstone and Magny-Cours, and notably drove in both GP2 and Formula One testing on the same day, making him the only person to have done so. He had previously been named Scuderia Toro Rosso's third driver for the 2006 F1 season alongside Scott Speed and Vitantonio Liuzzi, though he departed before securing a race seat.
Jani became the cornerstone of A1 Team Switzerland across multiple seasons of A1 Grand Prix. In the 2005-06 season, Switzerland earned the silver medal. He was absent early in 2006-07 before returning to win in Malaysia. Jani drove every race in the 2007-08 season, taking four wins and 168 points to claim the championship title for Switzerland. The team finished runner-up in 2008-09.
For the 2007 Champ Car World Series, Jani drove for PKV Racing, ending the season ninth overall with 231 points. He chose not to return for 2008 in favour of the A1GP season, and the Champ Car series was subsequently absorbed by the Indy Racing League.
Jani began his endurance career in 2010 with Rebellion Racing, partnering Nicolas Prost in a Lola-Judd LMP1 at the Le Mans Series and 24 Hours of Le Mans. He also raced in the FIA GT1 World Championship for Matech that year, in a Ford GT.
He raced full-time in the FIA World Endurance Championship from 2012 with Rebellion, teaming with Prost and Nick Heidfeld. In 2014, Jani joined the Porsche factory LMP1 programme. In his first season he took his maiden LMP1 win at São Paulo and finished third in the championship. The 2015 season brought another win at Bahrain and five second-place finishes, again yielding third in the standings.
The 2016 season opened with a win at Silverstone and a second place at Spa. At Le Mans, Jani and his Porsche co-drivers led late in the race and were gifted the overall victory when Kazuki Nakajima's leading Toyota suffered a catastrophic mechanical failure on the penultimate lap. It was one of the most dramatic reversals in Le Mans history, and the win cemented Jani's status among the top endurance racing drivers of his generation.
Jani entered Formula E for the 2017-18 season with Faraday Future Dragon Racing, partnering Jérôme d'Ambrosio. After two 18th-place finishes at the Hong Kong opener, he left the team, prioritising WEC commitments. He returned to Formula E for the 2019-20 season as part of Porsche's maiden campaign alongside André Lotterer, before being replaced by Pascal Wehrlein for the 2020-21 season.
In June 2023, Jani signed with Audi as a simulator driver to assist in developing their power unit ahead of their planned Formula 1 entry in 2026. Jani and his wife Lauren have a son together.
Neel Jani represents Swiss motorsport at its highest level, combining versatility — A1 Grand Prix champion, Le Mans winner, GP2 race winner, Champ Car competitor — with exceptional longevity in elite prototype racing. His 2016 Le Mans victory with Porsche, secured in the sport's most dramatic final-lap circumstances in decades, stands as the defining moment of a career that has spanned virtually every major form of motorsport.