Only goal difference is keeping Nottingham Forest outside of the relegation zone in the Championship table, as Brentford made it 11 games unbeaten in the league and moved into the play-off places.
Forest haven't won a league game since a 2-0 victory at home to Wycombe Wanderers on November 7. A superior goal difference of one keeps them above arch rivals Derby County in 21st place.
Story of the match
Brentford began the game strongly and could have taken the lead as early as the seventh minute when Emiliano Marcondes stole the ball in midfield and allowed The Bees to break with a four on two attack, Mathias Jensen played a pass through to Ivan Toney but the in form striker directed his shot narrowly wide of Brice Samba's goal.
The early scare for Nottingham Forest was a sign of things to come as Brentford broke the deadlock with a quarter of an hour on the clock. Rico Henry's corner found Henrik Dalsgaard at the near post, who powerfully headed across the goal and into the net, leaving Samba rooted.
Brentford almost doubled their advantage but a tremendous save from Samba kept the score at 1-0, Bryan Mbuemo lashed a volley destined for the back of the net after a sublime cross from Tariqe Fosu, but the Forest keeper parried the ball wide.
Marcondes then found Toney inside the box with an outswinging cross but his volley flashed over the bar. Forest were riding their luck but almost got back into it against the run of play. With five minutes remaining of the first half, Sammy Ameobi hit a fierce shot at goal, forcing David Raya into parrying it out and Harry Arter followed up, but again Raya was on hand to make the save, holding on to the ball.
A minute later, Forest were awarded a free kick just outside the box. Three players stood over the ball but it was Joe Lolley who took the shot on, but he could only blaze his effort over the bar.
In the second half, it was Forest who started the brighter. The strugglers looked better in possession, more comfortable and confident with the ball. Anthony Knockaert replaced Lolley at half time and he won a free kick on the edge of the box for the home side. Lyle Taylor stepped up and fired it hard and low, but Raya was well placed to make an easy save.
Moments later, Ameobi broke again and fired a drive cross across the face of the goal but nobody was there to turn it in. Brentford counter attacked and Henry again played in a brilliant cross to Fosu, who controlled the ball before turning and shooting, forcing an other great save from Samba who tipped it wide.
Forest did find the net on the hour mark, but Knockaert was adjudged to have been offside. It was a very late flag from the linesman, but the correct decision was made.
Raya was forced to rush off his line as Taylor burst through on goal to try and convert a loose ball, the striker was first to the ball but an incredible block from Mads Bech Sorensen kept the visitors lead in tact.
It was the Danish defender to the rescue again for The Bees, who blocked two shots from Cafu as Forest continued to cause big problems.
There were huge appeals for a penalty from the hosts, but it was a perfect last ditch challenge from Sorensen, yet again, that kept Forest out.
Then against the run of play, Brentford doubled their lead. Joshua Dasilva, on for Jensen in the 67th minute, cut in from the right and shot away from Samba to find the net at the corner.
Two minutes later, it was 3-0. Vitaly Janelt hit it long and Samba stayed on his line, leaving Toney to volley home first time which flew in low past the hapless Forest goalkeeper.
Forest found the net in injury time as Joe Worrall headed in leaving Raya furious with his defenders as the clean sheet was taken away from him after a particularly brilliant individual performance.
More drama ensued before the match was over. Knockaert, already booked for an earlier incident, was brought down in the area by Ethan Pinnock, but referee Geoff Eltringham booked him for the second time for simulation. There were little appeals from Forest, but the decision looked harsh and they will now be without one of their best players for the match against Sheffield Wednesday.
Despite the convincing score line, it was not as comfortable as it appeared to be for Brentford. The visitors controlled the first half significantly and the deficit could have easily been greater than one goal. However, Forest came out like a different team in the second half and Chris Hughton's substitutions made a big impact on the performance.
Joe Lolley was uninfluential again and was replaced at half time by Knockaert. The Frenchman was at the heart of almost everything Forest created, but Brentford ran away with the win after hanging on when one goal up, thanks largely in part to Sorensen's diehard attitude at the back.
Brentford look good value for promotion this season if they can keep the momentum going after the winter break, as they made in 11 games unbeaten. Although still a huge loss, it appears Ivan Toney is filling the void left by Ollie Watkins, last season's top scorer who left for Aston Villa in the summer.
Nottingham Forest: Samba, Ribeiro, Worrall, Figueiredo, Christie, Ameobi, Arter, Cafu, Lolley, Taylor
Subs: Mbe Soh, Smith, Bong, Jenkinson, Mighten, Guerrero, Sow, Knockaert, Swan
Brentford: Raya, Dalsgaard, Pinnock, Sorensen, Henry, Marcondes, Janelt, Jensen, Mbeumo, Fosu, Toney
Subs: Thompson, Canos, Dasilva, Jansson, Ghoddos, Daniels, Presley, Stevens, Haygarth