Brentford suffered their second successive home League One defeat as Rochdale came to town and left with the win.
The newly promoted side took the lead early on and although Brentford hit back through Robbie Simpson they scored twice in two minutes after the break to seal the win.
Even being reduced to ten men could not spoil Rochdale's day or deny them the victory they merited.
Rochdale started well, with lots of early possession, but The Bees had the first sights of goal.
Simpson had a header cleared off the line by Joe Widdowson from a Kevin O'Connor corner and Charlie MacDonald turned a Craig Woodman free kick wide soon after.
Rochdale opened the scoring with their first effort of note when a swerving long-range shot from Andrew Tutte was only palmed out by Alex McCarthy straight on to the head of Anthony Elding, and he had little problem nodding in from 12 yards.
The goal scorer, however, made an error soon after that looked at the time as if it may have turned the game.
Chris O'Grady attacked down the left and cut inside, his low shot was blocked by Leon Legge but Jason Kennedy turned the re-bound past McCarthy - it was rolling in but Elding touched it over the line from an offside position to give referee Simon Hooper little option but to rule it out.
Simpson headed over for Brentford but just before the half hour they were level.
Gary Alexander played a key role, feeding Myles Weston with a great ball, the wide man skipped past Scott Wiseman and pulled it back to Simpson, who scored from close range.
Brentford had the better of the game after the goal, and were in the ascendency before it, without creating many clear cut chances.
Gary Jones fired over for the visitors and Simpson headed wide again before the break and the goal scorer went close soon after when he was just unable to turn it a wickedly whipped Woodman free kick at the far post.
The first half had been intriguing without being enthralling with Rochdale's three-man midfield and pressing game making it difficult for Brentford to take complete control.
And the visitors came out after the break, stepped it up a gear and had sewn up the win just past the hour mark.
They were perhaps lucky to escape when Marcus Holness was only booked for pulling back Toumani Diagouraga when he appeared to be through on goal.
And Simpson curled the resulting free kick into the wall to ensure they weren't punished further.
But that aside, they were far and away the better team in the early stages of the second period, keeping the ball well and pulling Brentford's defence all over the place.
Legge made a vital block from an O'Grady shot and Jones shot wide but the goal wasn't long in coming and when it came it was a fine goal.
The Dale kept the ball for what appeared to be two or three minutes with pass after pass trying to find an opening, it eventually came on the left wide of the box where Widdowson fed O'Grady and he lashed in from 14 yards.
It got worse moments later when Tutte found space on the right, bundled his way past Woodman and crossed for Kennedy to turn it in from close range.
However, Kennedy's celebration was deemed excessive by Mr Hooper and he was shown a second yellow card to hand Brentford a lifeline.
They attempted to take it - Weston fired inches wide, MacDonald had a shot saved after a nice turn and Diagouraga blasted over.
But despite the introduction of Carl Cort and Nicky Adams, The Bees weren't creating as much as they would like.
Rochdale - with a two goal lead to defend - were happy to sit back with one man up front and allow Brentford to come at them.
The chances started to come as the minutes ticked by - Josh Lillis saved a Simpson header and Cort nodded an Adams corner wide.
Weston had a low shot saved and Cort headed a Woodman cross over at full stretch as Brentford pushed forward and Rochdale began to tire.
MacDonald and Simpson had a shots blocked and Cort headed wide but Brentford could not get the goal that would have set up a grandstand finish and Rochdale left with the points.
Brentford: McCarthy; O'Connor, Osborne, Legge, Woodman; Simpson, Bean (sub Cort 71 mins), Diagouraga, Weston; MacDonald, Alexander (sub Adams 64 mins)
Subs (not used): Lee, Balkestein, Spillane, Hunt, Forster
Rochdale: Lillis, Wiseman, Holness, Dawson, Widdowson; Tutte, Jones, Barry-Murphy, Kennedy, Elding (sub Akpa Akpro 82 mins); O'Grady
Subs (not used): Edwards, Redshaw, Done, Goodall, Andre
Bookings: Kennedy (18 mins), Holness (51 mins)
Sent Off: Kennedy (62 mins) (second bookable offence)
Attendance: 4,636 (229 away fans)
By Chris Wickham