A first half header from Michael Morrison and a late goal from Danny Green meant Brentford started 2012 with a derby defeat.
Central defender Morrison nodded in to give Charlton Athletic the lead and Green sealed Brentford's first defeat away from home since August.
Brentford started well, playing the ball around Charlton and utilising the extra man in midfield.
The home side struggled to get much of the ball and most of the first half was played with Brentford on the front, albeit Charlton's strong defensive line made it difficult for The Bees to find a way through.
But the home side improved after the break and their defensive resilience made sure Brentford had no way back.
Leon Legge had the first chance and almost scored his third goal of the Christmas period when he volleyed a corner narrowly wide while Jonathan Douglas, who bossed the first 45 minutes, had a pair of shots blocked.
The hosts&nbsp;were fortunate to escape when goalkeeper Ben Hamer punched out a Dale Bennett cross and was lucky to see it bounce of Morrison and back in to his arms.
Charlton had offered little going forward - Bradley Wright-Phillips curled a cross just past the far post and Richard Lee held on to a Green chip but when they took the lead it was very much against the run of play.
Brentford failed to get distance on a headed clearance of a Green long throw and when the ball was headed back, Lee slipped as he attempted to gather the bouncing ball allowing Morrison to beat him to it and nod it over him and in to the net.
The goal didn't really change the flow of the game but with a goal lead, Charlton were able to sit in and invite Brentford to break them down.
A Toumani Diagouraga shot deflected fortunately in to the arms of Hamer when anywhere else would have levelled the scores and McGinn's lobbed effort dipped inches wide.
A fierce Myles Weston shot was arrowing towards the corner before Leon Cort blocked it and the Charlton centre half headed narrowly wide at the other end.
Brentford would have considered themselves unfortunate to have gone in behind but they were almost out of it minutes in to the second half.
Yann Kermorgant headed the ball on and Wright-Phillips got past Legge, Lee slipped as he tried to come out but the Bees goalkeeper did enough to prevent the striker going round him and then watched as the Charlton top scorer lashed the loose ball well wide.
The home side were much improved after the break and could have wrapped the game up early in the second half.
Their best chances came in the air - Johnnie Jackson headed against a post from a corner and the home side could not force in the re-bound.
Kermorgant headed wide and Danny Hollands nodded another corner just wide at the back post.
Brentford had an opening when Niall McGinn fed Weston and the lay off fell to Marcus Bean but the midfield man fired wide from 20 yards.
Brentford introduced Gary Alexander and Sam Saunders and switched to 4-4-2 to attempt to regain the control they had in the first period.
And they were able to do it to some extent but Charlton's organisation meant there were few chances.
Saunders curled a free kick in to the wall, prompting appeals to referee Graham Scott it had been stopped by an arm, and then fired one over.
The home side could have sealed it when Kermorgant played in substitute Leon Clarke but Lee saved at his feet and Scott Wagstaff fired the loose ball over.
That almost came back to haunt the hosts when, following a series of passes on the edge of the penalty area, Douglas fed Clayton Donaldson but the striker fired over from six yards out under pressure from from Cort.
That proved to be crucial when Hamer kicked the ball long and Green had acres of space to cut in to the box, go round Lee and roll the ball in.
Brentford continued to fight - Douglas had a shot blocked and Hamer had to punch away a curling Saunders cross.
But there was no way back for The Bees as League One Champions-elect Charlton took the points.
Charlton Athletic: Hamer; Solly, Morrison, Cort, Wiggins; Green (sub Hughes 90 mins), Pritchard, Hollands, Jackson (sub Wagstaff 77 mins); Wright-Phillips (sub Clarke 78 mins), Kermorgant
Subs (not used): Sullivan, Taylor
Bookings: Solly (51 mins), Wiggins (77 mins), Cort (88 mins)
Brentford: Lee; Bennett (sub Dean 63 mins), Legge, Eger, Woodman; Bean (sub Alexander 63 mins), Douglas, Diagouraga; McGinn, Donaldson, Weston (sub Saunders 72 mins)
Subs (not used): Moore, Forrester
Attendance: 17,506 (1,186 Bees fans)
By Chris Wickham