Coventry City suffered late heartbreak at Griffin Park as David McGoldrick's early opener was cancelled out by a dramatic double from the Bees' Harry Forrester.
McGoldrick tortured Brentford's back line before opening the scoring after seven minutes but Forrester capitalised on a period of momentum for the hosts and got them back on level terms five minutes before the break before slotting home a penalty in the fourth of five minutes of added on time.
Boss Mark Robins made two changes to the side that lost 2-1 at the weekend at home to Notts County, bringing in Steven Jennings and Chris Hussey to replace James Bailey and Carl Baker in midfield.
After a lively start to the game it was the hosts who carved out the first half chance of the game after three minutes when Clayton Donaldson flashed a low cross across the City area with Harry Forrester's first touch at the back post only guiding the ball wide.
It was City who opened the scoring though after just seven minutes when a hooked ball from midfield from Franck Moussa found McGoldrick who beat the offside trap and was shepherded out wide by two defenders only to take them both on and fire low past Simon Moore from a tight angle.
It took the Bees until the 22nd minute to register an effort on target courtesy of a frre kick after Richard Wood was penalised for a foul on Forrester 20 yards from goal.
Jake Bidwell stepped up to take the set piece and nearly levelled for Uwe Rosler's side only to see his effort tipped around the post by Joe Murphy.
In a short spell of sustatined pressure by Brentford, Forrester's corner delivery then found Paul Hayes at the bak post only for him to fire his shot into the ground and watch the ball bounce over the bar.
Murphy was required again on 27 minutes when Donaldson got the better of Nathan Cameron on the right flank and swung in a cross for Jonathan Douglas whose header was tipped over the bar.
Harlee Dean was then denied from the resulting corner as he got behind Forrester's delivery and fired a hefty shot goalwards only for the ball to be stopped by a block from Cameron.
City got a grip back on the game soon after as a quick counter attack saw John Fleck lay off Jordan Clarke to fire an effort aimed inside the near post with Moore parrying away for a corner.
The Sky Blues were very nearly architects of their own downfall on 34 minutes though when McGoldrick tried to do too much with the ball up front and lost possession, Brentford then went on the counter-attack only to be stopped by Steven Jennings who sold a short backpass which Hayes intercepted.
The Bees striker fired from an angle just inside the area with Murphy getting enough on it to stop the ball going in as it trickled out for a corner.
Hayes then had Brentford's best chance of the game four minutes later when a poor pass from Moussa was intercepted and a cross was floated into the box, Hayes finding himself unmarked at the heart of the area but heading downwards and watching the ball bounce over the bar.
The equaliser the hosts were threatening came five minutes before the break though when Forrester latched onto a through ball in space and slipped a finish under Murphy.
The home side carried their momentum through after the break and could have taken the lead on the hour when a cross from Bidwell was met at the front of the area by Dean whose first time effort went wide.
City went straight up the other end though and nearly reinstated their lead through McGoldrick who dispossesed Douglas and tried to curl a shot into the top corner from the edge of the area only to be foiled by the fingertips of Moore.
Hayes spurned another opportunity with his header on 70 minutes after good work from Shaleum Logan allowed him to play a short ball to Donaldson whose floated cross found his strike partner with a free header from eight yards which he put over the bar.
It then took a last ditch tackle from Moussa to deny Forrester a second with 15 minutes to go after Logan's powerful cutback across the area, Forrester getting to the ball first but denied a goal by a tackle from Moussa.
Dean then sent a header wide from the resulting corner, diving at the ball but unable to keep it on target.
John Fleck went closer for Coventry with nine minutes to go when he picked the ball up in midfield and opted to shoot rather than pass, striking the post with a powerful 35-yard drive.
It all ended with heartbreak for City though as Brentford grabbed the winner in the fourth of five minutes of added on time from the spot.
The home side went on a late break which ended with Forrester being brought down in the area by Jordan Clarke, the wideman dusting himself off to slot home his and Brentford's second of the night to take all the points.
Attendance: 5,450 (770 Sky Blue Army)
Coventry City: Murphy, Clarke, Wood (c), Cameron, Reckord (Kilbane 59), Fleck, Jennings, Moussa, Hussey (Baker 45), Ball (McDonald 77), McGoldrick
Subs: Dunn (GK), McSheffrey, Christie, Edjenguele
Brentford: Moore, Forshaw, Craig, Dean, Douglas, Donaldson, Logan, Forrester, Diagouraga (Adeyemi 87), Hayes (Spencer 76), Bidwell
Subs: Lee (GK), O'Connor, Barron, Dallas, Legge
Bookings: Forrester (BRE)
Referee: K Stroud
Assistant Referees: D Cook, G Russell
Fourth Official: R Hodges