Mark Hudson rescued a deserved point for Cardiff City with a wonderful volley as Birmingham returned to the top six on goal difference.
Marlon King missed a second-half penalty but Erik Huseklepp put the home side in front against the run of play after a slick counter attack.
Captain Hudson converted Peter Whittingham's deft ball to equalise and Rudy Gestede almost grabbed a winner.
Chris Burke also forced a fine save from Cardiff keeper David Marshall.
The point leaves both sides locked together on 60 points, with Birmingham's vastly superior goal difference giving them the last play-off place with seven games remaining.
But Cardiff will feel they wasted a crucial opportunity to take maximum points from one of their promotion rivals, who looked totally devoid of ideas on a lively surface.
Birmingham struggled to pick up Cardiff's mobile midfielders throughout as Whittingham and Aron Gunnarsson found space at will in pockets in front of the home defence.
Did you know?
- Birmingham have not lost at St Andrews to Cardiff City since a 2-1 reverse in the old Second Division in December 1966
For all their dominance, though, the visitors failed to test Boaz Myhill in the home goal until substitute Gestede's drive eight minutes from time.
Joe Mason came closest to capitalising on their superiority in the first half when he flashed a drive across the face of Boaz Myhill's goal.
The lone striker, a summer recruit from Plymouth Argyle, was also within inches of reaching Whittingham's enticing cross.
Birmingham did force the only save of the first half when Guirane N'Daw's tame shot was comfortably saved by Marshall.
And after struggling so badly before the break, Birmingham were given the perfect opportunity to score when Jordan Mutch lured Don Cowie to dangle out a leg in his own area.
King, scorer of three penalties this season, stepped up but his weak effort was palmed away by Marshall as he dived to his right.
Cardiff's dominance continued, but they were caught out by a sucker punch on 68 minutes later for Birmingham's opener.
Chris Burke beat Kevin McNaughton, Cardiff's only defensive cover as they surged forward for a corner, and delivered a perfect ball for Huseklepp to stroke past Marshall at the far post.
Whittingham had looked Cardiff's most likely creator, and the midfielder showed his class once again this season to set up the equaliser 12 minutes from time.
Hudson still had plenty to do as he waited for Whittingham's chip over the home defence, but the captain controlled his side-foot volley to perfection from just inside the area.
Burke then tested Marshall's reactions with a sharp shot on the turn, before Cardiff's late surge saw Myhill saving Gestede's goal-bound effort.
Birmingham manager Chris Hughton said:
"We were not at our best in the first half. We got an improvement in the second half up against a team which floods the midfield.
"In 95 minutes their goal was the only chance they had."
Cardiff manager Malky Mackay said:
"I am disappointed because we played fantastically and showed real courage in dominating possession.
"If we had panicked after they had scored and lumped the ball forward it would have played into their hands.
"I thought we probed well, pushed on well after our equaliser and we had Birmingham on the back foot."
- 01 Myhill
- 04 Caldwell
- 05 Pablo (Gomis - 72' )
- 06 Ramage
- 24 Davies
- 07 Burke
- 08 N'daw
- 10 Huseklepp (Townsend - 69' )
- 12 Mutch
- 15 Elliott
- 09 King
- 13 Doyle
- 11 Townsend
- 14 Gomis
- 22 Redmond
- 19 Zigic
- 01 Marshall
- 02 McNaughton
- 03 Taylor
- 05 Hudson
- 25 Turner
- 07 Whittingham
- 08 Cowie (Gestede - 72' )
- 13 Lawrence
- 17 Gunnarsson
- 37 McPhail (Miller - 84' )
- 20 Mason
- 22 Heaton
- 23 Blake
- 09 Miller
- 10 Earnshaw
- 15 Gestede