Brentford 0 Birmingham 2
Clayton Donaldson scored against his former club and condemned Lee Carsley to defeat in his first game in charge of Brentford.
The former Bees striker chipped home Birmingham’s second in stoppage time after defender Michael Morrison’s header had given them a 71st-minute lead.
Alan Judge rattled the crossbar late on for the hosts but Carsley and his side were left frustrated with a second successive Championship defeat at home.
Carsley – promoted from development squad manager to head coach on Monday after Marinus Dijkuizen was sacked – made two changes and adjusted the formation from the side that lost to Sheffield Wednesday at the weekend.
Jack O’Connell replaced the suspended James Tarkowski while Ryan Woods came in for Josh Clarke, and Konstantin Kerschbaumer was moved to right midfield as Lasse Vibe joined Marco Djuricin up front.
Austrian Djuricin missed the target from close range twice in the opening 15 minutes and forced Birmingham keeper Tomasz Kuszczak into two low saves before the half-hour mark.
David Cotterill and ex-Bee Donaldson threatened at the other end but Judge also forced a decent save from Kuszczak at the end of a goalless first period.
The disappointing Kerschbaumer shot over just after the break before Vibe forced Kuszczak to save, but only Judge came close again when he rattled the bar on 87 minutes.
Morrison rose to power in a corner with 19 minutes left and after Bees committed players forward in search of a leveller, Donaldson broke clean through at the death before lifting the ball over goalkeeper David Button.
Brentford (4-4-2): Button; McCormack, O’Connell, Dean, Bidwell; Diagouraga, Kerschbaumer (Canos 69), Woods (Gogia 88), Judge; Vibe, Djuricin.
Subs not used: Bonham, Yennaris, Barbet, Udumaga, Clarke.