In-form Cavani gifts PSG win at Nancy
Lucas' free-kick gave the reigning champions a 13th-minute lead at the Stade Marcel-Picot with Cavani contributing his league-leading ninth goal shortly after on the artificial surface.
Former France international midfielder Alou Diarra pulled a goal back on his Nancy debut early in the second half as the 35-year-old appeared for his eighth club in the French top flight.
PSG climbed above Monaco on goal difference but Unai Emery's side still trail league leaders Nice by four points ahead of next Sunday's showdown with arch rivals Marseille.
"(Nancy) needed to win and were really motivated against us. We played as a unit, and the match required a lot of defensive effort to close it out. We didn't do everything well but we were good in defence," said Emery.
"Right now it's clear that Nice are very strong, but we'll keep making our way and we'll see."
Brazilian Lucas nudged the visitors ahead with his fifth goal of the season as his whipped delivery from out on the left wing nestled in the far corner after evading both Cavani and Nancy goalkeeper Guy-Roland Ndy Assembe.
Nancy captain Michael Chretien was at fault for PSG's second just five minutes later when he attempted to nod a long clearance from Alphonse Areola back to his own keeper.
The centre-back failed to spot a lurking Cavani, though, and the Uruguayan raced onto the loose ball and lifted a tidy lob over Assembe to continue his rich vein of goalscoring form.
With Basel making the trip to the French capital for Wednesday's Champions League encounter, PSG were reluctant to take any unnecessary risks and found their advantage halved on 55 minutes when Diarra connected with Benoit Pedretti's set piece.
But Nancy, who have scored just four goals in nine games, rarely looked like threatening again and PSG will now turn their focus to Europe ahead of next weekend's 'Le Classique'.
On Friday, Nice extended their unbeaten start under Lucien Favre with a 2-0 victory at home to 10-man Lyon.
Goals in either half from Paul Baysse and Jean Michael Seri ensured Nice continued their impressive early season charge, despite Mario Balotelli having a penalty saved late on.
Lyon slumped to a fourth defeat in nine matches after they were forced to play a man down for over an hour with Nabil Fekir dismissed for an ugly stamp on Baysse.
Martin Braithwaite scored twice as Toulouse roared back from a goal down to stun Monaco 3-1, far from ideal preparation for Leonardo Jardim's men ahead of Tuesday's trip to CSKA Moscow.
Valere Germain headed Monaco ahead with just three minutes gone in Toulouse, but the home side hit back through Oscar Trejo midway through the second half before Braithwaite completed the turnaround.