The visitors seemed to be heading for another frustrating result on their travels but came from behind to win after Edinson Cavani had levelled
During the first period the French champions were completely outplayed and the hosts merited their half-time advantage, which was given to them when Raphael Guerreiro scored from a tight angle.
But PSG were a different team in the second period and drew level when Javier Pastore's pass unlocked the defence and eventually resulted in Edinson Cavani scoring.
Substitutes Marco Verratti and Jean-Christophe Bahebeck then combined for the winning goal, with the young forward slotting home from a tight angle after a fine pass from the Italy midfielder.
Yet the home side came back into the game and created their first chances when Walid Mesloub and Yann Jouffre hit efforts wide in quick succession.
Suddenly on the front foot, Lorient continued to enjoy the majority of the possession, with Valentin Lavigne curling an effort just over the crossbar.
They then had a strong penalty appeal refused after Lavigne went down under a challenge from Lucas Digne.
Undeterred, Lorient continued to press forward and they were rewarded with a goal in the 42nd minute as Guerreiro got on the end of Jordan Ayew's clever pass to slot home at the end of a superb move.
PSG unsurprisingly emerged from the break with added purpose and almost levelled when Cavani missed the target after capitalising on the hosts' failure to clear one of a succession of corners.
However, the striker did not have to wait much longer to make his presence felt as PSG levelled in the 60th minute.
Javier Pastore was the architect, his chipped pass finding Thiago Motta - who slid a volley into the path of Cavani. The Uruguay international uncharacteristically scuffed his first effort, yet Lecomte's failure to hold onto the ball proved decisive as Cavani slotted in the rebound.
Marco Verratti was introduced immediately after the leveller and almost instantly made his presence felt by setting up the second.
The Italian's ball in behind the Lorient backline ran perfectly into the path of Bahebeck, who nipped in ahead of Lecomte and slotted home from a tight angle.
From there, Lorient never threatened to get back into the game, with PSG seeing the remaining minutes out without alarm.