Tarquini began karting in 1976 and progressed to Formula 3000 by 1985, spending three seasons with underfunded teams before making his Formula One debut in a one-off drive for Osella at the 1987 San Marino Grand Prix. His sole championship point came at the 1989 Mexican Grand Prix with AGS — a point he was controversially stripped of following a successful appeal by Williams and Scuderia Italia over their earlier Imola disqualification.
He raced across seven Formula One seasons with Osella, Coloni, AGS, Fondmetal, and Tyrrell, starting 78 Grands Prix and failing to qualify for 40 — 25 of those as outright pre-qualifying eliminations. Most failures resulted from racing cars that were simply too slow for the pre-qualifying sessions of the era, a format in which even faster entrants among the smaller teams were routinely eliminated. Contemporary observers considered him a talented driver let down by chronically uncompetitive machinery.
His final Formula One appearance came at the 1995 European Grand Prix with Tyrrell, substituting for the injured Ukyo Katayama. He was the last reigning British Touring Car Champion to compete in Formula One.
He holds the record for the most failed attempts to qualify in Formula One history (40).
Tarquini moved to Italian Superturismo in 1993, driving an Alfa Romeo to third in the championship. In 1994 he won the British Touring Car Championship at his first attempt in an Alfa Romeo, with the team's aerodynamic package generating considerable controversy. He returned to the BTCC in 1997 with Honda under Prodrive, finishing sixth in the standings, and raced in the series again in 2000.
After 2002 away from competition, Tarquini joined Alfa Romeo's ETCC effort in 2003 and won the title in his debut season with Nordauto — a pattern mirroring his 1994 BTCC success. He finished third in 2004 as the championship was won by Andy Priaulx in a BMW.
When the ETCC became the World Touring Car Championship in 2005, Tarquini continued with Alfa Romeo, winning two races. He then signed for the SEAT Sport works team for 2006, racing for the manufacturer through 2009. He finished runner-up to Yvan Muller in 2008 and then won the WTCC championship in the final race of 2009 at Macau, taking the title at age 47 — an achievement that set the record for the oldest FIA World Champion.
After SEAT's withdrawal from works WTCC competition, Tarquini raced for the SR-Sport and Lukoil-SUNRED teams through 2012, finishing runner-up in 2010 with five wins. He then drove for Honda under the JAS Motorsport banner from 2013 to 2015, taking multiple pole positions and podiums including Honda's first WTCC pole at the Race of Morocco. In 2016 he drove for the uncompetitive Lada team, managing two victories before the season ended.
Following the 2017 development season for the new Hyundai i30 N, Tarquini joined the WTCR — which merged the WTCC and TCR International Series — for 2018. He took the championship that year in a close battle with Muller, becoming the series' first champion at age 56. He announced his retirement from racing at the 2021 Race of Italy.
Tarquini has served as Sporting Director of Genesis Magma Racing for the FIA World Endurance Championship since 2026, overseeing the Genesis GMR-001 programme.
A 2005 Motor Sport magazine poll of readers ranked Tarquini the eleventh greatest touring car driver in history. His four major touring car titles — BTCC, ETCC, WTCC, and WTCR — across a span of 24 years make him one of the most durable and decorated saloon car racers in the sport's history. His Formula One career, while limited by circumstance, demonstrated enough ability that many considered him a victim of underfunding rather than a driver lacking the talent for a competitive seat.