The PA9 was a direct development of its predecessor, the PA8, continuing the lineage of Osella sports prototypes that traced their body shape back to the PA3. All PA-series sports cars shared a similarly designed monocoque architecture, with the PA9 distinguished primarily by its use of a 2-litre BMW engine sourced from Formula Two. The car represented a logical evolution of the existing PA series rather than a clean-sheet redesign, retaining the constructional philosophy that had served Osella well in earlier sports car programmes.
Between its introduction and retirement from major competition, PA9 chassis were registered fifty-nine times in sports car races, accumulating eight overall victories, nine class victories, and twenty-one podium finishes.
The PA9 made its racing debut on 5 April 1981 at the Autodromo Riccardo Paletti in Varano de' Melegari, with factory drivers Mauro Nesti and Carlo Franchi — who competed under the pseudonym Gimax — sharing duties across two chassis (numbers 103 and 104). Franchi achieved a podium finish in the very first race.
The second race brought an outright victory that surprised the motorsport world: factory drivers Giorgio Francia and Lella Lombardi won the Mugello 6 Hours, a round of the World Sportscar Championship, ahead of more powerful machinery including a Porsche 935K3 and a BMW 320i. At the 1000 Kilometres of Monza, the two factory PA9s finished second and third overall, and the works team repeated second and third finishes at the Pergusa 6 Hours.
Francia also took victories in the national Group 6 race at Vallelunga and in an additional race without championship status at Magione. Despite the strong results, Osella did not receive manufacturers' world championship points because the team had not registered for the manufacturers' standings.
The 1982 season brought greater financial pressure. Osella was simultaneously running a Formula One programme, which severely stretched resources. Results in sports car racing were less spectacular than 1981, though the team remained competitive in selected events. At the 1000 Kilometres of Monza, the works PA9 of Diulio Truffo and Luigi Moreschi retired after 158 laps with gearbox damage. At Silverstone, Francia and Truffo finished fourth; at Spa and Mugello, Francia and Moreschi finished sixth and fourth respectively. Class victories proved elusive as the Lancia LC1 — a considerably more powerful car — competed in the same Group 6 category.
A converted PA9, originally built as a PA8, was exported to North America during this period, where it was driven by Jacques Villeneuve senior in the Canadian-American Challenge Cup.
After the 1982 season, Osella withdrew its factory sports car team to concentrate on Formula One. Remaining PA9 chassis were sold to private operators. Swiss racing driver Alfred Baer acquired one example and competed in the Interseries, among other events. The last significant result for a PA9 in circuit racing was Tony LaRosa's second place at the Can-Am race at Summit Point in 1986.
However, the PA9 found its most sustained success in hillclimbing. Mauro Nesti, who had driven the car from its debut, went on to win the European Hill Climb Championship in the racing car class six consecutive times between 1983 and 1988 using his PA9 — a remarkable run of dominance that established both driver and car as defining figures of the era in European hillclimb competition.
The Osella PA9 stands as one of the most successful products of the Osella constructor, combining competitive results in top-level endurance racing during its first season with an extraordinary hillclimbing record that stretched across six seasons. Nesti's six consecutive European hillclimb titles with the car represent an achievement that few individual car-driver combinations have matched in any discipline of motorsport.