The first race, a 40-lap feature event, was won by ART Grand Prix driver Stoffel Vandoorne who started from fourth position.
Status Grand Prix driver Richie Stanaway won the second event, a 30-lap sprint race, ahead of Trident's Raffaele Marciello and Sergey Sirotkin of the Rapax team.
He had a small lead which was reduced because he was using super soft tyres which had higher degradation levels, allowing Rossi and Vandoorne to draw closer.
In the second race, Marciello began from pole position but lost the lead to Stanaway as a result of a slow start.
[2] The drag reduction system (DRS) had one activation zone for the race: on the main straight linking the final and first turns.
[9] Arthur Pic of Campos Racing lapped fastest with a time of 1 minute, 20.556 seconds, ahead of Rossi, Pierre Gasly, Vandoorne, Sergio Canamasas (MP Motorsport), Raffaele Marciello (Trident), Richie Stanaway (Status Grand Prix), André Negrão (Arden International), Haryanto and Norman Nato.
[10] Evans caused a brief early red flag period when he stopped his car atop a hill entering Massenet corner, and was unable to set a timed lap.
[10][11] Canamasas went onto the Sainte Dévote run-off area,[10] and Marco Sørensen (Carlin) locked his tyres, causing him hit the barrier at Rascasse corner,[11] and reversed out of the turn.
[3] Light rain fell as the session started and some drivers elected to equip the super soft tyres to their cars while other competitors chose to utilise wet-weather compounds.
[16] He shared the third row with Julián Leal of Carlin who was ahead of Hilmer Motorsport's Nick Yelloly and Jordan King of Racing Engineering.
[14][16] Artem Markelov followed in 13th, ahead of Stanaway whose front wing was damaged in a collision with the Mirabeau barrier, requiring him to enter the pit lane for a replacement nose cone.
[14][15] Negrão placed 15th, with Zoël Amberg in 16th who aquaplaned off the circuit because of an oversteer and struck the exit Tabac corner barrier, removing his right-rear wheel.
[14] Sørensen's car briefly launched airborne after mounting the kerbs through the swimming pool complex and qualified in 19th position.
[20] Maricello's super soft tyres began to degrade quickly, allowing Rossi and Vandoorne to draw closer over the next two laps.
King, who was delayed by a long queue of vehicles behind him, was the first driver to make a scheduled pit stop on the same lap and rejoined the track in clear air.
[20] On lap eight, Matsushita collided heavily with de Jong at the Novelle chicane, causing him to retire and was later penalised with a three-place grid penalty for the sprint race after the stewards judged him to have missed the corner's braking point.
[21][22] Marciello made his pit stop for new tyres on the next lap, allowing Rossi and Vandoorne to move into first and second and both drivers built an advantage over the rest of the field.
[20] Markelov retired from the race in the pit lane with damage to his car after running off the circuit, and drove over a kerb at the exit to the left-hand Louis Chiron corner, launching him airborne into a trackside barrier.
[21][23] The incident necessitated the activation of the virtual safety car (VSC) to allow track officials to clean the circuit.
He finished six seconds ahead of Rossi who slowed, with Leal third on the road, but was issued with a ten-second time penalty upon being judged by the stewards to have been unsafely released from his pit stall.
[19] The weather at the start of the race were cooler than the previous day's event with dark clouds in the sky and a chance of rain.
[25][26] Sørensen stalled in his grid position but was able to start soon after before he was issued with a ten-second time penalty because his mechanics were tending to his car after the 15-second signal was given.
[25][26] Nato was able to continue but made a pit stop for repairs and was issued with a ten-second time penalty because he was judged to have caused the collision.
[27] Leal was overtaken for fourth place by Canamasas at Sainte Dévote on the seventh lap's start and narrowly made the corner.
[26] Stanaway drifted at La Rascasse corner after his car's rear gave way and narrowly avoided a collision against a wall on the race's final lap.
Lynn, de Jong, Vișoiu, Markelov and Berthon followed in the next five places, while Binder, Negrão, Stöckinger, Matushita, Sørensen and Nato were the last of the classified finishers.
[25] The victory was Stanaway's first in the GP2 Series and the maiden triumph for his team Status Grand Prix following its take over of the former Caterham Racing entry.
[33] His team's managing director David Kennedy stated that it was "the best result that you can have in your maiden GP2 season" and praised Stanaway for demonstrating his speed and talent.
[33] The stewards imposed a three-place grid penalty on King for his role in the collision with Gasly, which he took at the season's next race in Austria.
Campos Racing remained in third position on 68 points, and moved further away from DAMS in fourth place, while Russian Time were fifth with eight rounds left in the season.