Martini won the 1983 European Formula 3 Championship in a racing car manufacturer Ralt. In 1984 he tried to enter the Formula 1 team Toleman, but failed at the Grand Prix of Italy at the qualification hurdle. In 1985 he got together with team manager Giancarlo Minardi in the premier class and was the first rider of the young team. End of the season he returned to the Formula 1 but first back to back, back around 1988 Minardi. He remained loyal to the team until 1991. In 1992 he drove for Dallara, but returned in 1993 back to Minardi, where he finished his career in 1995. Overall Martini drove 119 Grand Prix, of which 103 are for Minardi. His best race results were each a fourth place at the Grand Prix of San Marino and the Grand Prix of Portugal in 1991. Moreover, the Italians managed once in the front row ( at the U.S. Grand Prix 1990).
His biggest success in international motorsport celebrated Martini at the 1999 24 Hours of Le Mans. Together with Joachim Winkelhock and Yannick Dalmas he reached the overall victory on a BMW V12 Le Mans Roadster.
After his playing career was heard for a long time nothing of Martini. Only in 2006, his name appeared again in the media, as he played a race in the Grand Prix Masters series for former Formula 1 driver. At Silverstone he finished seventh among 16 participants.