Spaniard Ruben Rochina handed Rovers a deserved early lead from the penalty spot after David Murphy felled Mauro Formica but, crucially, Birmingham pulled level almost immediately courtesy of Marlon King's ninth goal of the season from close range.
Blackburn were undoubtedly the dominant side from the off.
Blues skipper Steven Caldwell denied Jordan Rhodes after Jack Butland had raced out of his area unnecessarily, before Rochina fired wide from 12 yards.
It was no real surprise when the hosts took the lead after 13 minutes.
Full-back Murphy brought down Formica in the area and Rochina stepped up to send Jack Butland the wrong way from the spot.
But Birmingham pulled level almost immediately with their first real attack.
Chris Burke's cross was met by a combination of former City defender Scott Dann and Wade Elliott and the ball fell to Nikola Zigic, whose effort came back off a post and King was on hand to tap home from two yards.
The goal inspired the visitors and Ravel Morrison brought a save out of Paul Robinson before King fired narrowly wide.
Rovers passed up a great chance to retake the lead from Rochina's corner as the game flowed from end to end. Danny Murphy struck the side-netting from distance on the half-hour mark before both sides saw goals rightfully ruled out for offside.
Zigic headed wide from Burke's cross at the start of the second half when the towering 6ft 8in Serbian should really have done better.
Rhodes was next to threaten at the other end as his header was cleared off the line by Blues defender Paul Robinson in impressive fashion.
Formica brought a good save out of England prodigy Butland with former Three Lions stopper Robinson showing what he could do to turn away Burke's effort from distance.
Robinson then tipped over Hayden Mullins' 81st-minute strike from 30 yards before substitute Fabio Nunes' impressive effort flew over amid a breathless conclusion to proceedings.
Dann came within inches of a late winner against his former employers but a point apiece was just reward.