Kossi Agassa denied St Etienne all three points at the death as plucky Reims took a point from a goalless draw.
Visiting goalkeeper Agassa endured some shaky moments as Les Verts dominated the creative play - ex-Leeds man Max Gradel at the heart of the performance - while opposite number Stephane Ruffier also remained resolute.
But it was Agassa who repelled Brandao's acrobatic effort deep into stoppage time to extend Reims' unbeaten run in Ligue 1 to a fifth game, and leave St Etienne without a league win in four attempts.
St Etienne started brightly, Pierre-Emerick Aubameyang controlling Gradel's cross before drilling the ball against Agassa after just two minutes of play.
The hosts raided forward again and Josua Guilavogui saw his audacious lob beat Agassa - but also the crossbar - following good work from Fabien Lemoine.
Only the linesman's flag saved Reims in the 27th minute, Guilavogui seizing on a poor clearance from Agassa to tee up Aubameyang for an easy tap-in, the tall striker caught out by the offside trap.
Reims came alive five minutes before the break as Antoine Devaux released Floyd Ayite in behind the home back line. Ruffier remained alert, though, sweeping the ball off the Togo international's boot just in time.
St Etienne were back on the offensive following the restart and Aubameyang should have done better as Romain Hamouma provided him with a sweet through-ball.
Gradel tricked his way into the area to find Lemoine but Agassa was fast to deflect the snapshot away for a corner.
The home pressure grew but Aubameyang could not keep his shot down when picked out in the penalty box by the impressive Gradel.
Ruffier did well to turn Grzegorz Krychowiak's effort round his post as Pape N'Diaye Souare caused havoc on the break, before Agassa repeated the trick at the other end as Brandao burst into the box.
And the Reims keeper would earn his side a valuable point in stoppage time as Brandao matched Aubameyang's superb cross.
The Brazilian connected perfectly with the ball but Agassa's magnificent save meant the visitors stayed alive at the Stade Geoffroy Guichard.