Ander Herrera and Kylian Mbappe put PSG on the way to a third straight league win with first-half goals.
Franck Honorat halved the deficit before half-time but Idrissa Gueye's long-range effort restored the visitors' two-goal advantage.
Steve Mounie forced a frantic finale five minutes from time and PSG had to endure some uncomfortable moments before substitute Angel Di Maria's cool last-gasp chip sealed the points.
PSG were without six-time Ballon d'Or winner Lionel Messi, who has yet to make his debut since joining from Barcelona.
Fellow forward Neymar and defender Sergio Ramos were also missing but Mauricio Pochettino still had the luxury of naming a star-studded bench.
Di Maria, Julian Draxler and Marquinhos were all among the substitutes, as was Italy goalkeeper Gianluigi Donnarumma, the summer signing from Milan.
Mbappe almost gave PSG a third-minute lead at the near post but was denied by a fine Marco Bizot save.
Marco Verratti went close to a first league goal since May 2017 but Herrera broke the deadlock after 23 minutes.
Brendan Chardonnet cleared Mbappe's cross to the edge of the area and Bizot pushed Herrera's volley onto the post, before the ball trickled across the line.
Mbappe doubled PSG's lead 13 minutes later with a superb follow-up header after Georginio Wijnaldum's shot had been blocked.
Romain Faivre's clever flick set up Honorat who fired under the body of Keylor Navas - the last thing the goalkeeper would have wanted in front of the watching Donnarumma.
Bizot made a similar hash of Gueye's effort and Mounie rifled home to give Brest hope before Di Maria had the final word.
Dominik Szoboszlai starred on his first RB Leipzig start as Stuttgart were swept aside 4-0 in the Bundesliga.
Szoboszlai scored twice - the first an angled beauty from 20 yards - as Leipzig bounced back from an opening-day defeat at Mainz.
The Hungary international opened the scoring seven minutes before half-time and Emil Forsberg doubled Leipzig's lead within 16 seconds of the start of the second half.
Szoboszlai grabbed his second six minutes later and Andre Silva settled matters from the penalty spot.
Real Betis and Cadiz drew 1-1 to repeat their results of the opening LaLiga weekend.
Alvaro Negredo put Cadiz ahead with an 11th-minute penalty but Juanmi levelled for Betis midway through the first period.