Marseille signed Bakambu during the winter transfer window to add firepower to Jorge Sampaoli's side and the move brought immediate dividends.
Bakambu, who scored 48 goals in 71 appearances for Chinese Super League club Beijing Guoan before his return to the French top flight, doubled the advantage on 76 minutes after Dimitri Payet had put the visitors in front with a first-half penalty.
Bakambu, a former Sochaux player, replaced Luis Henrique in the 74th minute.
After playing a one-two with Matteo Guendouzi, he was perfectly set up on the left side of the area and found the net with a left-footed shot from a tight angle.
Guendouzi was also involved in the opening goal.
The midfielder was pushed in the back by Facundo Medina after Cengiz Under rushed down the left flank and crossed the ball into the box.
Referee Stephanie Frappart pointed to the penalty spot and Payet — who was at the start at the move with a superb pass for Under — calmly sent goalkeeper Wuilker Farinez the wrong way.
It was Marseille's fifth consecutive away win.
Marseille are one point ahead of Nice, who play at Metz on Sunday.
Elsewhere on Saturday, Brest upset Lille 2-0 to return to winning ways and put an end to the defending champion's nine-match unbeaten run.
Brest's first win this year moved them up to 14th while Lille remained eighth.
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