The race was run as the XVII Grand Prix de Belgique over 36 laps of the 14.120 km Spa-Francorchamps circuit, a total race distance of 508.320 km. Daimler Benz AG entered three W196s for Fangio, Moss, and Karl Kling, running on Continental tyres. Scuderia Ferrari fielded Farina, Maurice Trintignant, and Paul Frère, with Harry Schell and Piero Taruffi also listed. The Officine Alfieri Maserati works team entered Luigi Musso, Jean Behra, Roberto Mieres, and Cesare Perdisa on Pirelli tyres, while private entries included Louis Rosier and Johnny Claes in Maserati 250Fs. The sole Lancia D50 was entered privately for Eugenio Castellotti by Scuderia Lancia. Vandervell Products brought the Vanwall VW 55 for Mike Hawthorn.
A procedural irregularity occurred with car number 4: Harry Schell had set a qualifying time, but Maurice Trintignant drove the car in the race. Piero Taruffi and Johnny Claes, the latter suffering an engine failure, did not start.
Castellotti set the fastest qualifying time of 4:18.1 in the privately entered Lancia D50, claiming pole position ahead of Fangio at 4:18.6 and Moss at 4:19.2. Farina was fourth at 4:20.9, Behra fifth at 4:23.6, and Kling sixth at 4:24.0. The gap between front and midfield was pronounced: Mieres qualified fourteenth at 5:09.0, more than 50 seconds off Castellotti's benchmark.
Castellotti, who had secured pole in the private Lancia entry, held the lead until retiring after 16 laps with gearbox failure. His withdrawal removed the one car capable of genuinely challenging Mercedes' pace. Jean Behra spun off in only the third lap; he later took over Roberto Mieres's car and drove the remaining 25 laps, the pair sharing the two championship points for fifth place under the rules then in force. Mike Hawthorn's Vanwall retired on lap 8 with gearbox trouble, and Kling was sidelined by an oil leak on lap 21.
With this opposition eliminated, Fangio and Moss were left entirely untroubled at the front. Fangio set the fastest lap at 4:20.6 and crossed the line in 2 hours 39 minutes 29.0 seconds, with Moss just 8.1 seconds behind. Farina in third had lost considerable time in a prolonged and ultimately unsuccessful attempt to pass Castellotti before the Italian's retirement, and finished 1 minute 40.5 seconds behind Moss. Paul Frère was a notable fourth place for Ferrari, becoming the first Belgian driver to finish in the points at his home race. Trintignant, driving Schell's car, completed the classified finishers in sixth.
The margin between the Mercedes 1–2 and Farina's third-place Ferrari exceeded two minutes — an illustration of the silver cars' advantage when their principal Lancia rival was removed.
Fangio's victory extended his lead in the Drivers' Championship to 19 points, clear of Trintignant on 11⅓ and Farina on 10⅓. Moss moved to 7 points with his second place. No Constructors' Championship existed at the time; that competition was not introduced until 1958.
The 1955 Belgian Grand Prix stands as one of the clearest demonstrations of Mercedes-Benz's dominance during their single season of Formula One competition. With the Lancia squad fielding only one private entry — which duly retired — there was no serious opposition to the W196's pace once Castellotti was out. Fangio went on to win the 1955 World Drivers' Championship convincingly, and Mercedes withdrew from all motorsport at the end of the season following the Le Mans disaster in June, just days after this race.