That recent form resulted in manager Terry Butcher being sacked in midweek and stand-in boss Andy Scott saw the side put in a tremendous second-half display which pushed Wrexham into deep trouble.
The Bees had a number of chances before they found themselves a goal down in the 40th minute. Sam Aiston crossed from the left and Neil Roberts headed back across goal for Chris Llewellyn to net.
Then Lee Thorpe saw his spot-kick brilliantly saved by home keeper Anthony Williams.
The outcome of the game might have changed completely, but just before half-time Llewellyn was clear but missed a chance of putting the home side two goals clear.
The second half was again all Brentford, but it wasn't until the 66th minute that Alan Connell connected with a right-wing cross from substitute Ricky Shakes to fire pass Williams.
In the 72nd minute Gary Smith put a through ball to Thorpe. He mis-kicked and home defender Steve Evans sliced the ball into his own goal to put the Bees in front.
In the 77th minute Wrexham were in a dreadful tangle with Connell getting three attempts before he finally netted to complete a great result for the visitors and bring despair for the home side, who were roundly booed off the field at the end.