The capital city side did just enough to bounce back from the previous week’s loss to Dijon.
The Argentine forward was quickest to react as Brest failed to clear the ball and scored with a shot into the top corner in the 85th minute for his ninth goal in 10 games in all competitions for PSG.
The win lifted the leaders and defending champions up to 30 points from 13 games, 10 ahead of Angers who were playing later on Saturday.
PSG goalkeeper Sergio Rico turned away a curling effort from Mathias Autret and had a lucky escape when he sent a clearance straight to Yoann Court whose first-time shot bounced wide of the post.
Court missed another chance by sending his shot into the side-netting.
PSG made the most of their luck by taking the lead in the 39th minute although they had VAR to thank.
Julien Draxler’s through ball found Angel Di Maria who speed away from his marker and dinked the ball over Gautier Larsonneur.
The linesman raised his flag but the decision was overturned two minutes later by VAR and the goal awarded.
Rico made another good save in the second half to deny Romain Perraud before substitute Samuel Grandsir scored a deserved equaliser for Brest as PSG were caught on the break.
PSG coach, Thomas Tuchel, threw on three substitutes in the 80th minute, with Icardi replacing Edinson Cavani, and was quickly rewarded.
Edited by Dianabasi Effiong/Felix Ajide