Trulli's parents were motorsport fans who named their son after Finnish Grand Prix motorcycle champion Jarno Saarinen. He excelled in karting from an early age, winning the Karting World Championship in 1991 and taking multiple Italian and European karting titles through to 1995. He graduated to single-seaters by winning the German Formula Three Championship in 1996, marking him as one of Europe's most promising young talents.
Trulli made his Formula One debut with Minardi in 1997. After seven races, he was called up to replace the injured Olivier Panis at Prost, where he immediately impressed — finishing fourth in Germany and briefly leading at Austria before his engine failed. He stayed with Prost for 1998 and 1999, scoring his first podium at the 1999 European Grand Prix under wet and chaotic conditions. The Prost car was not consistently competitive, however, and Trulli moved to Jordan for 2000.
At Jordan, Trulli continued to deliver strong qualifying performances without adding to his podium tally. His reputation as a qualifying specialist grew during this period, a characterisation he disputed but which stuck. His long-term manager Flavio Briatore — also Renault's team manager — secured him a move to the Anglo-French team for 2002.
At Renault, Trulli partnered first Jenson Button and then Fernando Alonso. He regularly outqualified both teammates over race weekends despite Alonso taking the team's first win in Hungary in 2003. Trulli achieved a podium at the 2003 German Grand Prix, his first since Prost.
In 2004, Trulli was the better of the two Renault drivers for the first half of the season. His victory at the Monaco Grand Prix — from pole position, controlling the race from the front — was the high point of his Formula One career and one of the finest performances of his driving life. Following a last-corner error in France that cost a podium and enraged team boss Briatore, his relationship with the team deteriorated. He was sacked three races before the season ended, despite leading Alonso in the championship at that point, and replaced by Jacques Villeneuve. He had already signed for Toyota and joined them early for the final two races of 2004.
Trulli spent five seasons at Toyota. Early in 2005, he took Toyota's first Formula One pole position at Indianapolis, though the race was not held for the majority of entrants due to the Michelin tyre safety crisis. He typically outperformed his well-paid teammate Ralf Schumacher in qualifying. A third-place finish in France in 2008 was among his best results for the team. In 2009, a memorable drive at the Bahrain Grand Prix saw him qualify on pole and record the only fastest lap of his career, finishing third.
Toyota withdrew from Formula One after the 2009 season.
Trulli moved to the newly formed Lotus team (later renamed Team Lotus) alongside Heikki Kovalainen. The team was a back-of-the-grid outfit and he scored no points in either season. Ahead of 2012, the team was renamed Caterham F1, and Trulli was replaced by Vitaly Petrov in February 2012. His exit left Formula One without an Italian driver for the first time since 1969.
Trulli competed in the inaugural Formula E season in 2014–15 with his own team, Trulli GP. The team withdrew from the 2015–16 season after failing to pass technical scrutineering.
Trulli is married to Barbara, and they have three children: sons Enzo (born 2005, named after Trulli's father) and Marco (born 2006), and daughter Veronica (born 2014). He is co-owner of a vineyard in the Abruzzo region of Italy and produces his own wine. His son Enzo has pursued a career in motorsport, progressing from karting through F4 UAE and FIA Formula 3.
Trulli is remembered for two things in near equal measure: his unmatched qualifying ability in machinery that rarely matched the front runners, and the "Trulli Train" phenomenon — the line of faster cars stacking up behind him during races when he deployed his defensive driving to extraordinary effect. His Monaco win in 2004 was a complete performance from start to finish that stands as proof of his genuine speed. The circumstances of his dismissal from Renault — sacked while leading his world-champion-to-be teammate in the standings — remain one of the more puzzling decisions of the era.