Walter Pandiani came off the substitutes' bench to halt the Manchester United bandwagon and grab a priceless point for Steve Bruce's relegation-threatened side in this 2-2 draw.
Pandiani, who is on the verge of joining Espanyol for £1million, turned home his second Premiership goal of the campaign with 12 minutes remaining.
United had twice led through Ruud van Nistelrooy and Wayne Rooney, had the chances in the second-half to kill off the game but Blues never gave up and gained only their fifth home point of the campaign.
Alex Ferguson's side are now 11 points adrift of Chelsea after their single-goal win at Manchester City.
Birmingham are still in deep trouble, but this will be an enormous confidence-booster against a United side who had taken 22 points from the previous eight games.
City are at least now showing signs of not surrendering their top flight status without a fight after a performance branded as "pathetic" by Bruce at Manchester City only 11 days ago.
They matched the Red Devils in the opening 45 minutes with a committed performance and Emile Heskey caused plenty of problems to the United rearguard.
In the second-half United stepped up a gear, with Rooney a constant threat, and they had opportunities to have wrapped up the points in more comfortable fashion. But Bruce's battlers refused to buckle.
It took United only four minutes to break the deadlock through van Nistelrooy's 17th goal of the campaign.
Paul Scholes played a telling ball into the path of Kieran Richardson and the full-back had time to steady himself before sending over a low centre and van Nistelrooy held off the challenge of Matthew Upson to drill his shot past Maik Taylor.
The Blues retaliated and Scholes pulled off a point-blank range clearance to somehow keep out Stephen Clemence's header after Heskey had flicked Jermaine Pennant's corner across the face of goal.
The home side were showing plenty of spirit after their early setback. Edwin van der Sar reacted well to hold on to a 35-yard free-kick from Jiri Jarosik low to his right before Blues deservedly equalised after 19 minutes.
United appealed in vain for a foul by former United midfielder Nicky Butt on Cristiano Ronaldo and Birmingham broke away in incisive fashion down the left.
Jamie Clapham and Jarosik combined, Emile Heskey turned the ball back into the path of Clapham and his low shot contained too much power for Van der Sar.
The visitors were temporarily rattled and Jarosik again went for glory from another long-range free-kick and he was only a yard too high with a curling effort.
United still threatened and Scholes spotted the run of Van Nistelrooy and threaded a perfect pass into his path but he drilled his shot straight at Taylor.
Birmingham were knocking the ball around with a confidence which belied their lowly league placing and Heskey was a constant threat up front.
Rooney had a quiet opening half-hour and his first attempt at goal contained plenty of power but flew past Taylor's post.
United began to enjoy more of the possession in the closing minutes of the half and van Nistelrooy hit the inside of the post after combining with Rooney, but had drifted offside.
Taylor was fortunate after spilling the ball when coming to the edge of his area but he was able to recover before van Nistelrooy could pounce.
Rooney went close for the first time in the game when he spun past Martin Taylor on the edge of the box and fired a rasping shot only a yard wide but he made no mistake in the 53rd minute.
Alan Smith sent over a low teasing centre, van Nistelrooy allowed the ball to run through to Rooney, who calmly clipped it wide of 'keeper Taylor into the corner of the net.
United were now enjoying more of the possession and van Nistelrooy screwed a shot across the face of goal after racing onto a Rooney pass.
Ronaldo had the chance to wrap up the points for United after being played in by Van Nistelrooy but he sliced his shot across the face of goal.
Rooney was only inches off target with a sublime chip as Maik Taylor scrambled across his goal line after evading the challenge of Martin Taylor.
Bruce brought on Pandiani for Pennant and within three minutes the striker had brought the Blues back on level terms.
Neil Kilkenny's free-kick found its way to Damien Johnson at the far post and he managed to turn the ball back across goal where Pandiani made no mistake.
Ole Gunnar Solskjaer was introduced by United for the final six minutes – his first senior action for 19 months after severe knee problems - but City held on.
