Modena began racing in karts, winning the Italian junior karting championship in 125cc. He contested two seasons in Italian Formula Ford before joining Euroracing in the Italian Formula Three series in 1985, placing 15th. Switching to Team Seresina's Reynard chassis for 1986, he scored three wins, finished fourth overall, placed second in the Monaco support race, and won a European series round at Imola. He also took pole position at the Macau Grand Prix that year.
In 1987, Modena joined Onyx for the International Formula 3000 series and won the championship in his debut season, claiming three round victories.
Modena's raw speed attracted immediate Formula One interest. Brabham gave him a one-off drive at the 1987 Australian Grand Prix, where he qualified 15th but retired before mid-distance after stopping three times for tyres and ultimately succumbing to exhaustion with the unfamiliar turbocharged BMW engine. For 1988, he raced for the new EuroBrun team, whose Ford Cosworth-powered ER188 was uncompetitive, though Modena consistently outpaced teammate Oscar Larrauri.
When Brabham returned from a sabbatical in 1989, Modena was offered a seat alongside Martin Brundle. Using Pirelli qualifying tyres, he frequently qualified inside the top ten despite the Judd V8's limitations. His first podium came with third place at the Monaco Grand Prix. In 1990, Brabham faced severe ownership problems following the imprisonment of Joachim Luthi for fraud, and results were scarce, though Modena finished fifth at the season-opening United States Grand Prix.
Modena's best Formula One opportunity arrived in 1991, when Tyrrell signed him as Jean Alesi's replacement. The team ran 1990-specification Honda engines and Pirelli tyres on a developed version of the proven 020 chassis. He qualified on the front row at Monaco alongside Ayrton Senna and ran with the McLaren before being delayed in traffic, then suffering a violent engine failure. At the Canadian Grand Prix, he was rewarded with second place after Nigel Mansell retired on the final lap. However, Pirelli's difficulty in developing a consistent race tyre — combined with the heavy Honda engine and a chassis originally designed for the lighter Cosworth DFR — hampered the rest of the season, and Modena scored only one further point, for sixth in Japan.
He moved to Jordan for 1992, but the team's Yamaha V12 engine was underpowered and Modena struggled throughout the year, failing to qualify for four races. Relations with the team deteriorated; Jordan designer Gary Anderson later noted that the failed qualifying attempts eroded Modena's motivation and his temper made it difficult for him to recover composure. He scored the team's only point of the season at the final round in Australia but could not secure a drive for 1993.
Modena raced in Italian and German touring car categories from 1993 to 1999, driving for Alfa Romeo. He won occasional races but was never a serious title contender. He spent 2000 with Opel before retiring from competitive motorsport.
After retiring from racing, Modena took part in karting endurance events. From 2003 he worked for Bridgestone, testing road and racing tyres across numerous countries in Europe, Asia, Oceania, the Middle East, and the Americas.
Modena was known for eccentric habits during his Formula One career — he would not allow his car to be parked on the left side of the garage, would not permit anyone other than his designated team member to touch the car once he was strapped in, and was known to exit and re-enter the car before the warm-up lap if he saw unauthorised contact. He also habitually wore his driving gloves inside out, a habit he attributed to preference rather than superstition.
Modena has lived in Rome since the late 1990s with his wife, former actress Sveva Altieri. They have two children: Ascanio, an archaeologist and journalist, and Vittoria, a jurisconsult.
Modena's career illustrates the fine margins of Formula One opportunity. A dominant Formula 3000 champion who showed genuine brilliance — particularly at Monaco in 1991 — he never found the right package consistently enough to convert his speed into sustained results. His touring car years with Alfa Romeo demonstrated continued competitiveness, but his Formula One chapter, particularly that 1991 season with Tyrrell, remains the most vivid evidence of what might have been.