Match ends, Brentford 2, Aston Villa 1.
Aston Villa slipped out of the Championship play-off places after defeat at Brentford extended their winless run to five games.
Romaine Swayers put the Bees in front with a low 20-yard drive but Josh Onomah headed Villa level by half-time.
But Lasse Vibe fired home from six yards after Villa failed to clear a corner to seal Brentford's win.
Steve Bruce's side slip to eighth after Sheffield United and Middlesbrough won, three points outside the top six.
But more worrying for Bruce is the fact that Villa have not won this month, taking only three points from a possible 15 since beating Ipswich at Villa Park on 25 November.
And with games against Boro and Bristol City looming in the next week, he will have also been concerned by the loss of top scorer Albert Adomah to injury early in the first half.
Brentford, who have now lost only twice in their past 17 league matches, controlled much of the game and Sergi Canos saw a shot palmed away by Villa keeper Sam Johnstone before Sawyers capitalised on Glenn Whelan losing possession to fire them in front.
Villa, who have won only one of their last 22 away games on Boxing Day, soon levelled when Onomah headed in Brentford old boy Scott Hogan's cross from six yards but the Bees picked up the pace after the break.
It needed a last-ditch challenge from Tommy Elphick, making his first league start of the season, to deny Canos after the Spaniard's shot bounced off him and deflected goalwards.
And, after Vibe put the home side back in front, Canos was denied a third when his curling effort came back off the bar.
Villa put the Bees, who remain in mid-table, under late pressure but substitute Keinan Davis had a shot parried wide and Hogan saw an effort cleared off the line in stoppage time as the hosts held on to extend their unbeaten home run to 11 league games - their best run in the top two divisions since 1951.
Brentford boss Dean Smith told BBC Radio London:
"We were good value for the win. I didn't think there were lots of clear-cut chances. Given the conditions, you felt there was going to be a lot more chances than there were.
"I think it's the character of the players at the moment, you see Andreas [Bjelland] has got a nasty cut on his head, came off and came back on.
"Chris Mepham had blood coming out of his nose, came off and came back on, so the lads are pulling together to get these results now."
Aston Villa manager Steve Bruce told BBC WM:
"Everything about our performance with and without the ball was loose. We weren't aggressive enough with the ball or without it.
"I thought performances like that had left us, but unfortunately it's crept back in again and we have to eradicate it.
"I don't think it's an attitude thing or a work-rate thing. With Aston Villa there comes an expectation and, at the minute, you have to handle the expectation."
- 29BarbetBooked at 41mins
- 10McEachranBooked at 37minsSubstituted forMokotjoat 69'minutes
- 21VibeSubstituted forMaupayat 82'minutes
- 34Bech Sörensen
- 24ElphickBooked at 68minsSubstituted forEl Mohamadyat 85'minutes
- 6WhelanSubstituted forDavisat 67'minutes
- 37AdomahSubstituted forOnomahat 18'minutes
- 2de Laet
- 27El Mohamady
- Keith Stroud
- Shots on Target
Second Half ends, Brentford 2, Aston Villa 1.
Offside, Aston Villa. Alan Hutton tries a through ball, but Robert Snodgrass is caught offside.
Attempt missed. Romaine Sawyers (Brentford) right footed shot from the left side of the six yard box is close, but misses to the left. Assisted by Nico Yennaris following a corner.
Attempt missed. Nico Yennaris (Brentford) header from the centre of the box misses to the left. Assisted by Sergi Canos with a cross following a corner.
Corner, Brentford. Conceded by Scott Hogan.
Corner, Brentford. Conceded by Neil Taylor.
Attempt saved. Keinan Davis (Aston Villa) left footed shot from very close range is saved in the centre of the goal.
Attempt blocked. Scott Hogan (Aston Villa) right footed shot from the centre of the box is blocked. Assisted by Josh Onomah.
Corner, Aston Villa. Conceded by Daniel Bentley.
Attempt saved. Keinan Davis (Aston Villa) left footed shot from the centre of the box is saved in the bottom left corner.
Sergi Canos (Brentford) wins a free kick in the defensive half.
Foul by Alan Hutton (Aston Villa).
Corner, Aston Villa. Conceded by Nico Yennaris.
Neal Maupay (Brentford) wins a free kick on the right wing.
Foul by James Chester (Aston Villa).
Delay over. They are ready to continue.
Substitution, Aston Villa. Ahmed El Mohamady replaces Tommy Elphick.
Delay in match Andreas Bjelland (Brentford) because of an injury.
Andreas Bjelland (Brentford) wins a free kick in the defensive half.