It seemed as if the home side would have to settle for a draw, but two goals in the final 10 minutes of the game helped them to a vital home victory
Portuguese midfielder Paulo Machado gifted the hosts the lead early on when he found the net from inside the area, but Younes Belhanda restored parity halfway through the second half. Leandro Greco and Kostas Mitroglou then added their names to the score-sheet in the closing stages of the game to help the hosts to victory.
The Greek giants started the match the better side and needed only four minutes to open the scoring. Greco danced past his marker down the left before sending in a low cross for Mitroglou, who saw his shot hit the upright. Machado was alert, though, and tapped home from close range to make it 1-0.
Mitroglou then came close to doubling his side's lead after some sloppy defending from Mapou Yanga-Mbiwa. However, Montpellier goalkeeper Geoffrey Jourdren pulled off a superb save to bail out Yanga-Mbiwa and deny the prolific attacker.
Montpellier, meanwhile, were unable to really threaten Olympiakos, and their only serious chance of the first half came after a long ball from Hilton around the half-hour mark. Souleymane Camara escaped the attention of his marker, but his volley from a difficult position was off target.
The home side again threatened in the opening stages of the first half, with Djamel Abdoun, Greco and Mitroglou all looking dangerous. Nevertheless, Jourdren rushed off his line to prevent the latter from getting a shot in, while Yanga-Mbiwa made a fine interception to avoid a second Olympiakos goal.
La Paillade then took over the initiative and created a number of dangerous chances within the space of a few minutes. Roy Carroll first denied Jonathan Tinhan with a good reflex, before the experienced shot-stopper did well to collect Joris Marveaux's header from close range.
There was little Carroll could do to stop Belhanda's attempt in the 67th minute, though, as the referee had no option but to award the away side a spot kick after Dimitris Siovas pulled down Camara inside the area. The playmaker had no trouble slotting home from the spot.
The Piraeus side were not too impressed and almost restored their lead right from the kick-off. Nevertheless, some fine defending from Henri Bedimo prevented Machado from netting his second of the game.
Olympiakos kept on pushing and were eventually rewarded in the 80th minute. The Montpellier defence allowed Greco too much space after a corner kick, and the winger fired home from inside the area to make it 2-1.
Things would only get worse for the French champions from here on, and Mitroglou made it three only minutes later. A fine cross from Jose Holebas reached the prolific attacker, who volleyed past the helpless Jourdren after escaping Yanga-Mbiwa's attention.
Olympiakos sit third in their section with six points from four games. They resume Champions League action on November 22 away against Schalke.
Montpellier remain last in their group with only one point. Their next match in Europe is the trip to Arsenal in two weeks' time.