Daryl Murphy celebrated his return to the Republic of Ireland squad with his ninth goal of the season as Town stayed firmly in the Play-Off hunt.
The striker, who joins up with the Irish for the first time in six years for their friendly against Serbia on Wednesday, converted Frank Nouble’s cross seven minutes before the break to give Town three vital points.
Paul Taylor twice went close to adding to the score in the second-half, while Paul Anderson was also denied by Darren Randolph late on.
Jonny Williams missed out on his debut after sustaining a knock in training yesterday, with Taylor for Stephen Hunt the only change to the side that went down at Leicester last weekend.
Lee Novak fired well wide in the game’s first opening, Nikola Zigic then almost getting in on the Town backline before Aaron Cresswell cleared the danger.
Brilliant defending by Christophe Berra robbed Federico Macheda of a gilt edged chance on 12 minutes after the frontman broke clear from Zigic’s header.
Paul Green’s header was cleared by Will Packwood as Town responded, but the visitors continued to carry an early threat on the break, Novak bringing the ball down on the edge of the box but dragging his shot wide.
Frank Nouble forced a corner down the right, Taylor then weaving his way past two Birmingham defenders in the box but Aaron Martin blocked his path.
Berra couldn’t make his header count from Cresswell’s free-kick, then good work by Taylor conjured up an opening that was dealt with by Packwood.
Darren Randolph saved from Nouble before Town got the breakthrough on 38 minutes, Nouble’s cross touched in at the far post by Murphy.
Good work again by Berra prevented Macheda getting his shot in, while Randolph had to be alert to gather Nouble’s cross at the nearpost as the first-half came to an end.
Birmingham made a change at the start of the second-half with Liverpool loanee Jordon Ibe on for Paul Callis.
Jay Tabb did well to get on the end of Taylor’s cross, his header saved by Randolph, another delivery from Taylor stretching the Birmingham defence, with Martin clearing.
Town were forced into a change six minutes after the restart, Nouble limping off to be replaced by Anderson.
Blues threatened a second when Taylor cut inside and curled a right foot effort that seemed destined for the far corner until Randolph stuck out his left hand.
Taylor was giving Birmingham problems when he had the ball on the left, cutting inside at will, the frontman curling another effort just wide of Randolph’s goal.
Chris Burke replaced Macheda just before the hour and the substitute set up what should have been the equaliser, his cross leaving Novak a tap in at the far post but he sent the ball high over the bar.
Luke Chambers followed Taylor’s lead, cutting in from the right to send a left footer just wide before Stephen Hunt replaced Tabb for the last 20 minutes.
Randolph, who had a stormer at St Andrew’s in the reverse fixture, saved his team again when he kept out Anderson’s close range effort after the wideman had intercepted a backpass.
Novak made way for Brian Howard in Lee Clark’s last throw of the dice, but Town could have sealed the win a minute later, Cresswell getting on the end of Paul Green’s cross but Randolph was in the right place to deny the full-back.
Taylor left the field to a standing ovation from the home crowd two minutes from time, the signing from Peterborough having played his part in a vital three points as Blues begin a crucial month.