The Uruguayan, who scored the winner at Valenciennes on Wednesday, sealed the victory 11 minutes from time with his fourth goal of the season after centre back Marquinhos had put the French champions ahead four minutes before the break.
PSG started the game with a revamped team as Ezequiel Lavezzi, Cavani and Blaise Matuidi were all rested ahead of their Champions League Group C home clash against Benfica on Wednesday.
Four days after labouring at Valenciennes, they again struggled to create chances despite dominating the possession until Marquinhos broke the deadlock by tapping home the ball from close range.
Cavani, who replaced Zlatan Ibrahimovic midway through the second half, converted a penalty the referee had awarded for a foul on him although Toulouse centre back Uros Spajic had clearly gone for the ball as he slid in to tackle.
PSG climbed to top on 18 points from eight games, one ahead of Monaco, who visit midtable Stade Reims on Sunday, and third-placed Olympique Marseille, who won at 2-0 Lorient in the day's early game thanks to goals from Mathieu Valbuena and Andre Ayew.
(Reporting by Gregory Blachier; Editing by Clare Fallon)
