Edinson Cavani and Jean-Christophe Bahebeck secured the points at Stade Yves Allainmat on Saturday, their second-half strikes coming after Raphael Guerreiro had put Lorient in front.
All eyes were on PSG as they attempted to close the four-point deficit on leaders Marseille, whom they meet next week.
It seemed as though Laurent Blanc's men would be frustrated after Lorient belied their 17th-placed league position to take control of the opening period.
But Cavani, back in the starting XI having served his suspension for a bizarre red card against Lens, levelled in the 60th minute - before launching into the trademark mock gun-fire celebration that had led to that sending off against Antoine Kombouare's men.
PSG took control from that point and moved to within a point of Marseille, albeit having played a game more, thanks to Bahebeck's cool 68th-minute finish.
Blanc's side started more brightly and could have taken the lead twice inside the first 10 minutes, Benjamin Lecomte producing fine saves to deny Lucas Moura and Ezequiel Lavezzi.
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.
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