Dean Smith did not get the birthday present he was hoping for after Blackburn took all three points from Griffin Park, despite being down to 10 men for most of the second half.
Shane Duffy fired the away side into the lead 85 minutes in after skipper Grant Hanley was sent off for picking up two yellows in what was a poor performance from both sides.
Smith handed new loan signing Leandro Rodriguez his debut while Sam Saunders replaced John Swift in the starting line-up.
After a stop-start opening it was Saunders who had the Bees’ first chance of the game 17 minutes in when Alan Judge’s cross found the winger, but his volley was blocked by what looked like a hand on route to goal.
Brentford got themselves a free kick in the 28th minute and built two walls in front of the Blackburn defensive wall and it nearly worked a treat, but Yoann Barbet’s strike was palmed away by Jason Steele.
Balckburn would have been celebrating an opener 39 minutes in when Hope Akpan connected with the ball at the back post, but David Button was on hand to produce yet another fine save to tip the ball over the bar.
Griffin Park erupted into life 56 minutes in when Grant Hanley received his marching orders after picking up a second yellow card for deliberately handling the ball, and Brentford started to exert some previously unseen dominance onto the game.
Blackburn reorganised into two banks of four with Danny Graham playing the lone forward role but Brentford were getting chances, albeit from distance – Alan McCormack’s drive from outside the bus found its way onto the Ealing Road.
The away side were proving difficult to break down, and Smith introduced Sergi Canos 68 minutes with the hope his added flair could break down a stubborn Blackburn defence.
There was some good news for Brentford however, when Scott Hogan made his home league debut after 18 months out injured in the 75th minute.
Blackburn somehow then took the lead in the 85th minute when Shane Duffy found himself with the ball and space in the Bees box and rifled his shot into the roof of the net, sending the travelling fans into a frenzy.
The fourth official added five minutes of added time, enough time for Jake Bidwell to send a free header wide and for Steele to pull of a fine diving save from an Alan Judge strike.