Eager to atone for their home defeat to Monaco last week and aiming to avoid going winless in their opening four games for the first time since 2007, PSG could scarcely have asked for a better start.
Joao Neves fed Ousmane Dembele on the edge of the box, and he picked out Ferran Torres, who finished first-time into the bottom corner from all of 25 yards after just five minutes.
The ever-dangerous PSG frontline was purring early in this one, and Dembele forced a super save from Egil Selvik, who parried into the path of Khvicha Kvaratskhelia, but the Georgian superstar could only drag wide.
The hosts, who were mourning the passing of legendary manager Eric Roy, took until after the quarter-hour mark to really threaten.
When they did, Pathe Mboup fizzed over the bar from the edge of the box before Ludovic Ajorque glanced an inviting delivery from Kenny Lala just wide.
Luis Enrique lost influential right back Achraf Hakimi to injury midway through the half, and this seemed to stunt his side in an attacking sense as they adjusted to their new formation.
To Brest’s credit, they kept the reigning European champions at bay and limited them to a Kvaratskhelia effort that was tipped over the bar by Selvik.
Five minutes after the restart, the usually-reliable Nuno Mendes almost cost his side as his loose pass on the edge of his own box was seized upon by Kamory Doumbia, and his effort beat the onrushing Matvey Safonov but not the post.
The busy opening to the second half continued as PSG thought they had doubled their lead when Bradley Locko put it through his own net, but it was chalked off as the Brest defender had been pushed by Warren Zaire-Emery.
Locko then influenced the game at the other end moments later when he picked out Doumbia, whose powerful header looked destined for the bottom corner but Safonov got down low to his left to make a stunning save.
The Parisiens’ defence was creaking and only a perfectly-timed interception in his own six-yard box from Willian Pacho spared Zaire-Emery’s blushes after he was robbed by Mboup.
A clearly frustrated Luis Enrique made a pair of attacking changes, and both of those subs almost made an immediate impact.
Maghnes Akliouche made headway down the left, and his teasing ball across the middle was met by a sliding Neves, who was denied by a desperate save from Selvik.
Brest ensured it wouldn’t be a comfortable end to the game with Safonov again repelling Mboup but, ultimately, PSG held on for a three points, which was their second of the week after dismantling Slovan Bratislava in midweek.
They will look to build on this ahead of Le Classique against Marseille next week. Brest, meanwhile, will take plenty from this despite suffering a first defeat of the season.
Flashscore Man of the Match: Matvey Safonov (Paris Saint-Germain)