Second-half goals from Ollie Watkins and Neal Maupay clinched victory for Brentford, who are now unbeaten in eight league matches.
Watkins’ composed penalty on 74 minutes and substitute Maupay’s shot from the centre of the box with six minutes remaining gave the visitors a deserved three points.
Both sides had chances in the first half, but neither could make the breakthrough.
The Bees enjoyed success down the left flank with Watkins setting up Lasse Vibe on the edge of the box, before Josh Clarke found Kamehelo Mokotjo, but neither could find the target.
Just before the break Maikel Kieftenbeld almost put the home side ahead with a stunning strike from 35 yards which cannoned off keeper Daniel Bentley’s right hand post.
The decisive moment came after a crude foul on Maupay by Michael Morrison, and Watkins coolly placed his penalty into the bottom left-hand corner.
Maupay wrapped things up when he fired past Kuszczak in front of the travelling fans.
Maxime Collin, who featured for Birmingham along with fellow former Brentford man Jota, was stretchered off after nine minutes.
Brentford (4-3-3): Bentley; Dalsgaard (sub Barbet 65), Bjelland, Egan, Clarke; Mokotjo; Sawyers, Woods; Watkins, Vibe (sub Maupay 69), Jozefzoon (sub Canos 85)
Subs not used: Daniels, McLeod, McEachran, Mepham.
This post was last modified on 01/11/2017