Mass made his Formula One debut at the 1973 British Grand Prix with Surtees, making sporadic appearances before achieving a full-time seat in 1974.

In his final season with McLaren in 1977, having taken several podiums with the team, Mass finished a career-best sixth in the World Drivers' Championship.

He was seriously injured at the 1980 Austrian Grand Prix, bruising his neck and fracturing vertebrae as his Arrows A3 rolled over during practice.

Following his crash with Mauro Baldi at the 1982 French Grand Prix—only two months after his involvement in the death of Gilles Villeneuve—Mass retired from Formula One, having achieved one win, two fastest laps and eight podiums.

Outside of Formula One, Mass entered 12 editions of the 24 Hours of Le Mans from 1972 to 1995, winning in 1989 alongside Manuel Reuter and Stanley Dickens, driving the Sauber C9, as well as finishing runner-up in the World Sportscar Championship, matching his result from 1984.

He won one GP race (1975 Spanish Grand Prix), secured no pole positions, achieved 8 podiums and scored a total of 71 championship points.

On 8 May 1982, with only 10 minutes left until the end of the qualifying session for the 1982 Belgian Grand Prix at Zolder, Villeneuve collided with Mass while attempting to overtake him.

His seat was dislodged and he was flung from his car, landing heavily among the catch fencing at the opposite side of the track.

In 1972, he teamed up with Hans-Joachim Stuck to drive a Ford Capri RS2600 to victory at the Spa 24 Hours endurance race in Belgium.

He finished second to Clay Regazzoni and Arturo Merzario in a November 1972 9-hour race at the Kyalami Circuit, in Johannesburg, South Africa.

[2] Mass, driving a Surtees TS-15, tied with Jean Pierre Beltoise in qualifying for the Jim Clark Memorial Formula Two auto race in April 1973 held at Hockenheim, both drivers recording times of 2 minutes, 2.8 seconds, for an average of 124.3 miles per hour.

[6] Mass won the 1975 Spanish Grand Prix after leader, Rolf Stommelen's car hit a protective barrier, exploded into flames and catapulted into the crowd at the Montjuich circuit.

[7] Merzario and Mass led an Alfa Romeo sweep of the first two positions in the 1975 Coppa Florio manufacturers championship automobile race at Pergusa.

His March and the Arrows of Baldi touched at maximum speeds, both cars flying off the track and through a containment fence.

Mass and Bobby Rahal combined to win the Champion Spark Plug Grand Prix at the Mid-Ohio Sports Car Course in Lexington, Ohio.