And with the hosts battling for league survival, they took full advantage despite going down to 10 men as Che Adams saw red in the 23rd minute.
After Joel Coleman saved a first-half penalty from Lukas Jutkiewicz, Jonathan Grounds put the Blues ahead before the break with Craig Gardner adding a second from the penalty spot on 76 minutes.
Have a look below at the Huddersfield Examiner's key talking points from today's game at St Andrew's.
Jonathan Grounds goal just before half-time gave ten-man Birmingham City something to hold on to for the second 45 minutes.
Moan of the Match
Too many of Huddersfield Town’s ‘second string’ failed to take their chance, arguably making David Wagner’s Play-Off selection slightly easier.
After a shaky start, has Martin Cranie done enough to stake his claim as a central defensive option going followed?
Man of the Match
Tweet of the Match
Michael Jones (Chester) - couldn’t argue with either penalty decisions and although Birmingham City’s red card may have looked harsh, was still justified.
One of the only times this season that the travelling Blue White Army were out-sung by their hosts.
It’s a loss but with Play-Offs already secured, the main aim is to get the players fresh and prepared for the Play-Offs, with Philip Billing ’s injury potentially a massive blow.