Young striker Jahmari Clarke made himself a Royals hero as he bagged two second-half goals to give Reading their first win in five matches.
A depleted royals squad, without their manager Veljko Paunovic, went a goal down after three minutes as Scott Hogan stole the ball from Liam Moore’s back pass to put the Blues in front.
But the Royals hit back as half-time substitute Clarke came to the rescue as the 18-year-old forward scored his first goal for the club.
Clarke then added to his goal by scoring the winner as he knocked the ball in from close range after Andy Yiadom sprung forward on a counter attack.
Reading are in 16th after 17 matches in the Championship heading into the latest international break. Reading had the boost of Andy Yiadom returning to the starting eleven as he took the place of Tyrell Ashcroft after an impressive Championship debut from the 17-year-old.
The Royals were still without manager Paunovic, who is still serving a term of isolation after a positive covid test.
It was a delayed kick-off at St Andrews with the match starting at 3.30pm, half an hour later than scheduled, due to technical difficulties at the turnstiles.
It was a disastrous start for Reading, who started slowly and gifted Birmingham the chance to race into an early lead after three minutes.
Captain Liam Moore completely under hit his attempted back pass to Luke Southwood, and Blues striker Scott Hogan snatched the loose pass, rounded the goalkeeper and tapped the ball into the empty net.
Birmingham had the better of the game in the early stages having taken the lead as Riley McGree had a dipping volley that missed the target before Southwood punched away a dangerous Hogan cross.
The visitors tried to push forward in hope of salvaging an equaliser but Andy Yiadom’s gut-busting run was in vain as he was flagged offside after he was picked out by Tom Dele-Bashiru.
Reading had a half shout for a penalty in the 24th minute when Yiadom threaded the ball through for George Puscas, but Mitch Roberts slid in to get enough on the ball and dispossessed the forward.
The Royals’ best chance came from a set piece when Josh Laurent was brought down 25 yards from goal, leaving top scorer John Swift the chance to strike.
But his disappointing effort struck the wall as the chance passed them by, before Dele-Bashiru smashed a shot well off target.
There were a host of yellow cards for the home team in the first-half as Jeremie Bela, Harlee Dean and Marcel Oakley were all booked but they went in a goal up at the break.
In charge in the absence of Paunovic, assistant manager Marko Mitrovic made a switch at half-time as young striker Jahmari Clarke replaced Puscas.
The Blues picked up a fourth card as McGree was booked for pulling the shirt of Ejaria.
Chances were few and far between for both sides in the opening 20 minutes of the second period as McGree had a half chance but missed the target for Birmingham.
Yiadom looked to be Reading’s most potent attacking threat as he got down the right and threw a cross in the middle, but it was cleared by Dean before Clarke could latch onto it.
Reading then had a chance from the resulting corner but after Moore’s header, Dele-Bashiru lashed a shot off target.
Having shown some attacking intent, the Royals were rewarded with an equaliser in the 70th minute as substitute Clarke netted his first senior goal.
Swift swung in an inviting cross and Clarke glanced the header past the keeper into the far corner to level.
There was a scare in the 78th minute for Reading as the Blues hit the frame of the goal as Troy Deeney was denied by the post. A late change saw Mamadi Camara come on for the final 10 minutes as Dele-Bashiru was replaced.
With the game in the balance, the Royals got their noses in front as Clarke capped off a dream half as he pounced from close range.
A driving run from Yiadom got Reading on the front foot, he delivered the ball into Swift whose shot was saved, but Clarke was there to spring onto the rebound and finish from a few yards out.
Birmingham applied pressure late on into four minutes of stoppage time as they threw bodies forward into the box, but Reading held on to stop a run of four consecutive defeats.
Birmingham City: Sarkic, Roberts, Dean (c), Mitch Roberts, Oakley, Bela, Sunjic, Gardner, McGree, Hogan, Deeney Subs: Etheridge, Castillo, James, Aneke, Woods, Walker, Jutkiewicz
Reading: Southwood, Yiadom, Dann, Moore (c), Holmes, Rahman, Laurent, Dele-Bashiru, Ejaria, Swift, Puscas Subs: Rafael, Ashcroft, Abrefa, Camara, Osorio, Clarke, Ehibhatiomhan
Goals: Hogan 3′, Clarke 70′, 82′
