Goals from Gary Madine and veteran defender Ian Harte meant there was no repeat of last season’s opening-day defeat to the Bees.
The Brentford defence was given a torrid time by Carlisle’s energetic front line and debutant Craig Curran struck the woodwork twice in the first six minutes.
First he sent a looping header onto the bar from James Berrett’s accurate cross and then poked a rebound against the foot of a post after keeper Simon Moore had saved his initial effort.
Carlisle finally went ahead in the 22nd minute when left-back Sean McDaid fired low into the heart of the penalty area and Madine had time to get the ball under control and beat Moore with a shot from eight yards.
And then on the stroke of half-time, Curran was fouled just inside the area by Kevin O’Connor and Harte sent Moore the wrong way from the penalty spot.