Brest remained looking over their shoulder at the Ligue 1 relegation zone after losing at home to Toulouse tonight.
Landry Chauvin's side headed into this game five points above the drop zone and looking to build on last weekend's 1-1 draw with title-chasing Lyon.
But Adrien Rabiot's goal on the stroke of half-time at the Stade Francis-Le Ble - coupled with a 5-1 win for Evian against Sochaux - saw Brest's margin over the bottom three shrink to just two points. TFC, meanwhile, climbed to 11th.
The home team created the game's first chance after three minutes, but Toulouse goalkeeper Ali Ahamada made the block after Florian Raspentino had unleashed a low drive from Benoit Lesoimier's through-ball.
The visitors soon found their feet, though, and mustered a couple of decent opportunities of their own before forging ahead.
Etienne Didot freed Franck Tabanou inside the penalty area for a close-range right footed shot that Alexis Thebaux deflected away, and then Eden Ben Basat released Adrien Regattin on the edge of the penalty area for a left-footed volley that was again kept out by the Brest goalkeeper.
Thebaux was beaten just before the break, though, when Rabiot latched onto Tabanou's pass and despatched a sweet left-footed shot home for his first Ligue 1 goal.
Brest emerged all guns blazing after the interval and had the lion's share of the chances but were unable to find a way past Ahamada.
Jonathan Ayite fed Bruno Grougi on the edge of the box for a low blast which rustled the side-netting in the 55th minute, and Larsen Toure went within inches of scoring moments after his introduction midway through the second period when his ferocious right-footed volley from fellow substitute Magaye Gueye's assist fizzed just wide.
Bernard Mendy also had a sight of goal for the hosts seven minutes from time when Ousmane Coulibaly's pass found him in space on the edge of the area, but he sent his right-footed attempt narrowly over the bar and TFC left with all three points.