Fernando Alonso made the most of a dry Monte Carlo street circuit to take the P1 slot in what was a busy final 10 minutes.
It was a very slow start to the session with just one lap completed in the first 40 minutes which belonged to Valtteri Bottas.
The reason for the delay was that the rain had fallen in the break between sessions and no one wanted to run on a wet track.
When the running did begin it was on the intermediate tyres with Jenson Button leading the way on a 1:31.594.
But a swap to the super softs in the final ten minutes - and for most of the drivers a first run out on track in the afternoon - saw the lap times tumble.
Alonso finished quickest of all with a 1:18.482 while Lewis Hamilton came through at the very end to take second, 0.419s down.
Sebastian Vettel was third quickest in his Red Bull racer, 0.535s off the pace while Jean-Eric Vergne claimed an impressive fourth ahead of Bottas and Sergio Perez.
Only one driver failed to see the chequered flag on Friday afternoon which was Ferrari's Kimi Raikkonen.
He ran into trouble early in the session with his Ferrari stuttering around the circuit on his first serious flying lap. He limped back into the pits and the team revealed he "won't run anymore in this session."
He had completed just four laps when his day's work came to an end with a gearbox issue.
Meanwhile, Marcus Ericsson brought out the yellows late on but was able to get going in his Caterham.
01 Fernando Alonso Ferrari 1:18.482 15 laps
02 Lewis Hamilton Mercedes 1:18.901 +0.419 12 laps
03 Sebastian Vettel Red Bull 1:19.017 +0.535 15 laps
04 Jean-Eric Vergne Toro Rosso 1:19.351 +0.869 14 laps
05 Valtteri Bottas Williams 1:19.421 +0.939 9 laps
06 Sergio Perez Force India 1:19.668 +1.186 9 laps
07 Nico Hulkenberg Force India 1:19.712 +1.230 10 laps
08 Jenson Button McLaren 1:19.721 +1.239 16 laps
09 Daniel Ricciardo Red Bull 1:19.779 +1.297 11 laps
10 Kevin Magnussen McLaren 1:20.230 +1.748 16 laps
11 Felipe Mass Williams 1:20.394 +1.912 8 laps
12 Daniil Kvyat Toro Rosso 1:20.622 +2.140 13 laps
13 Adrian Sutil Sauber 1:20.811 +2.329 8 laps
14 Pastor Maldonado Lotus 1:20.977 +2.495 7 laps
15 Esteban Gutierrez Sauber 1:21.467 +2.985 8 laps
16 Romain Grosjean Lotus 1:21.700 +3.218 6 laps
17 Kamui Kobayashi Caterham 1:21.924 +3.442 6 laps
18 Jules Bianchi Marussia 1:21.937 +3.455 13 laps
19 Max Chilton Marussia 1:22.683 +4.201 13 laps
20 Nico Rosberg Mercedes 1:22.862 +4.380 11 laps
21 Marcus Ericsson Caterham 1:23.164 +4.682 6 laps
22 Kimi Raikkonen Ferrari 1:45.509 +27.027 4 laps
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