There were no changes in the entry after the Belgian GP and so it was business as usual at Monaco where the three leading Honda-engined cars were at the front as usual with Nigel Mansell taking pole in his Williams, Ayrton Senna second in the Lotus and Nelson Piquet third in the second Williams. Alain Prost was fourth for the McLaren-TAG team with Michele Alboreto fifth in his Ferrari. Sixth place was a surprise in the form of Eddie Cheever's Arrows-Megatron while the top 10 was completed by Stefan Johansson (McLaren-TAG), Gerhard Berger (Ferrari), Thierry Boutsen (Benetton-Ford) and Riccardo Patrese (Brabham-BMW). Alboreto had a spectacular crash when he ran into the back of Christian Danner's Zakspeed on the climb after Ste Devote. The Ferrari flew through the air but fortunately landed back on the track. With 26 cars starting at Monaco for the first time there were worries about safety in the race.

At the start Mansell went straight into the lead so there was no chance of a repetition of his collision with Senna at Spa. The Brazilian was second with Piquet third ahead of Alboreto, Prost and Cheever. The order at the front remained unchanged until lap 30 when Mansell slowed with a loss of boost pressure. Senna went into the lead and stayed there all the way to the flag, despite stopping for tyres. Piquet stayed second while Prost moved to third, overhauling Cheever who ran third for much of the mid-race. In the closing laps Alain suffered an engine failure and so third place went to Alboreto with Berger fourth (after Cheever went out with engine failure), Jonathan Palmer fifth in his Tyrrell and Ivan Capelli sixth in the Leyton House March.