On-loan Tottenham midfielder Mark Yeates was the scourge of the Bees, destroying the home side with a strike in either half.
To put it simply, the Brentford side who have raced to the top of League One with some solid performances, failed to turn up this afternoon.
Perhaps it was the lunchtime kick-off or perhaps it was the Bees bearing late festive gifts to a Colchester side who are comfortably in the play-off positions.
But whatever led to Martin Allen's side's first defeat for several weeks, he will want them to return to winning ways as soon as possible.
The U's arrived at Griffin Park having only lost three times on their travels, and were the first side to settle. Brentford were warned of Colchester's intentions from as early as the 13th minute when Greg Halford and Chris Iwelumo combined, but Stuart Nelson was able to push Iwelumo's 15-yard drive for a corner.
Midway through the first half, Yeates found a willing Jamie Cureton whose cross found the head of Iwelumo, but he was unable to guide his effort onto the target.
The U's were ahead on 30 minutes when Yeates collected the ball on the left and with Kevin O'Connor defending, there seemed to be little danger. Yeates however beat O'Connor and let fly a low powerful drive which went in at Nelson's near post, to the dismay of the home crowd.
For all their possession Brentford found little in the way of penetration as any high ball's aimed to DJ Campbell or Lloyd Owusu were easily dealt with by Wayne Brown and Liam Chilvers at the heart of the visitors' defence.
When Campbell did have an effort on target, Aidan Davison was on hand to thwart any danger, Davison having an excellent game in the Colchester goal.
Late on in the first half the keeper was alert to an Owusu header to frustrate the Bees again.
The U's, Yeates in particular, were in rampant form but once again Nelson was there to deny the midfielder in the 67th and 71st minutes.
Yeates however was not to be denied and he doubled his and Colchester's advantage seven minutes before the final whistle.
Davison had just denied Ed Hutchinson and Owusu, who hit the Colchester post and then an upfield punt by Davison found Yeates in the clear and he was to make no mistake in finding the net to send the Essex boys home happy.