The race was won by Ayrton Senna in the McLaren.Nigel Mansell finished in second place, scoring his first points of the season.Mansell's team-mate, Riccardo Patrese, ran in third place until crashing on oil dropped by Stefano Modena, whose engine expired just ahead of him.Alain Prost finished in fifth position after being delayed by a slow late-race pit stop.
Ayrton Senna shocked no-one by taking pole position, but second place was a surprise with Stefano Modena taking full advantage of the superior Pirelli qualifying tyres to be second, followed by Patrese, Piquet, a disappointed Mansell, Berger, Prost, Moreno, Alesi, and de Cesaris. Alex Caffi had a huge accident in the swimming pool section on Saturday, after missing Thursday qualifying with a gearbox problem, and did not participate in the race. Elsewhere Martin Brundle was excluded for missing a weight check in Thursday practice.
At the start, Senna got away well followed by Modena, Patrese, Mansell, and Prost. In the usual first corner mayhem Berger ran into the back of Piquet, dropping the Austrian to the back of the pack and breaking Piquet's suspension, Berger would later crash out. Senna quickly built up a huge lead over Modena and Patrese. Meanwhile, Andrea de Cesaris in the Jordan was eventually catching up to Jean Alesi and just outside the points in 7th place before retiring shortly after battling with the second Ferrari with a sticking throttle. Meanwhile, Aguri Suzuki in the Lola hit the wall at St. Devote on lap 25 with braking problems, as Modena's teammate Satoru Nakajima had spun and retired at the Nouvelle Chicane after making contact with Martini. Stefano Modena was blocked for a few laps by Emanuele Pirro in the Dallara who ignored blue flags, leading to BBC Commentator James Hunt saying "This is disgraceful driving by Emanuele Pirro". Most of Senna's chasers were eliminated on lap 42 when Modena's engine blew in the tunnel, spreading oil on the track which caused Patrese to crash. Alboreto also retired with engine failure at the same time. Just after taking 10th place from Eric Bernard, Blundell's Brabham lost control because of the oil from Modena's Tyrrell and crashed at the chicane. Senna now had a huge lead over Prost and Mansell, but the Englishman passed Prost with a daring move going into the chicane, and eventually started flying despite having problems earlier in the race. Prost would later pit to repair a damaged wheel causing a slow puncture, but the stop was very long and he dropped down to fifth.
Senna won his fourth Monaco Grand Prix in five years by 18 seconds over Mansell, Alesi, Moreno, Prost, and Pirro. The second-place finish was Nigel Mansell's first points of the season. Curiously, as Senna was slowing down after finishing the race, the pit crew mistakenly ordered him to take another lap, believing that he had crossed for the final lap.
