Salvatore Sirigu tipped a low free kick from Valbuena around the post in the 12th. The PSG goalkeeper then saved a volley from Jordan Ayew in the 21st and denied Valbuena's effort from the rebound.
Thiago Motta then put his team in trouble while chesting a cross. The ball got away from him, Valbuena intercepted it and got kicked in the foot by the PSG midfielder.
Andre Ayew fired the ball into the roof of the net for the opener in the 34th.
That goal seemed to wake up the PSG players, and Mandanda was forced to punch away a volley from Ibrahimovic in the 41st.
The Marseille goalkeeper came off his line late and could not prevent Maxwell from leveling the match just before halftime.
The hosts failed to capitalize on their numerical superiority in the second half despite a swerving shot from Marseille winger Dimitri Payet parried by Sirigu in the 63rd.
Two minutes later, Mandanda palmed away a header from PSG defender Alex and Andre Ayew's poor judgment gave PSG an opportunity to take the lead.
Marseille slipped to fourth place, level on points with Lille.
In Montpellier, Victor Hugo Montano opened the scoring for the hosts in the 17th and Anthony Mounier doubled the lead by heading home a corner from Remy Cabella on the stroke of halftime.
Alexandre Lacazette pulled one back for Lyon with a long-range strike in the 48th minute, but Remy Cabella converted a penalty in the 60th to make it 3-1 after Lyon goalkeeper Anthony Lopes had brought Montano down.
Cabella slipped the ball past Lopes in the 66th and Montano headed in Cabella's cross in the 68th to round off the scoring.
Lyon midfielder Maxime Gonalons was sent off in the 82nd after picking up a second yellow card.
Montpellier snapped a five-game winless streak to climb to eighth place.
Lyon has been a contender for a Champions League spot in recent seasons, but its poor start this year leaves the side 10 points behind league leader Monaco after nine games.
"The second half was a string of unbelievable and unforgivable mistakes," Lyon coach Remi Garde said. "Some players tonight did not have the level required to play in the league."
Lyon has won only one of its last 11 matches in all competitions.
Roy Contout put Sochaux ahead by slamming the ball under the bar in the 17th. But Bordeaux forward Henri Saivet equalized from the penalty spot in the 21st after Sochaux goalkeeper Simon Pouplin had fouled Cheick Diabate.
Jussie headed in a cross from Mariano to give Bordeaux a 2-1 lead. Diabate sealed the win with a low strike in the 70th and a chip in the 89th.
The result leaves Sochaux in 19th place.
Monaco beat Saint-Etienne 2-1 on Saturday to keep the lead.
Also Saturday, it was: Lille 3, Ajaccio 0; Toulouse 1, Nice 0; Nantes 3, Evian 0; Guingamp 2, Rennes 0; and Valenciennes 1, Reims 1.
On Friday, Bastia routed Lorient 4-1.
