Lee Carsley’s first game in charge of Brentford, after stepping in to replace the sacked Marinus Dijkhuizen, ended in a 2-0 home defeat, as the Bees were stung by Birmingham.
The visitors went into this match without a league victory in three games, but returned to winning ways with goals from Michael Morrison and Clayton Donaldson.
Three points lifts Gary Rowett’s side up to fifth place on goal difference and leaves Carsley facing a tough challenge at the wrong end of the table.
The only other game in the Championship was at Craven Cottage where Fulham were beaten 3-0 by Wolves.
Tom Cairney’s early red card gave the Midlanders a numerical advantage and three second-half strikes sent them home victorious.
Adam Le Fondre netted the opener before Liverpool loanee Sheyi Ojo and James Henry completed the scoring.