The Midlands club, often playing second fiddle, scrambled to a draw with a last-minute equaliser from on-loan Lee Bowyer.
Birmingham's performance was often disjointed against a Cardiff side which has emerged as strong promotion candidates under the guidance of the astute David Jones.
They appeared to be heading for victory with a smartly taken goal on the hour from skipper Joe Ledley who scored for the second successive game, but Birmingham salvaged some pride with their somewhat fortunate equaliser.
Ominously Cardiff are rapidly closing the gap on Birmingham, who have scored only four goals in their last seven games.
Cardiff, unbeaten in their previous nine games, demonstrated why they are the Championship side in form with some positive attacking play which was generally spearheaded by their well-built striker Jay Boothroyd.
He proved extremely difficult to knock off the ball and his goalscoring potential became an increasing worry to the home defence.
In their desire to make an impression, the much changed Birmingham side adopted an early attacking policy with former Cardiff striker Cameron Jerome catching the eye with a couple of early efforts.
Unfortunately this enthusiasm quickly faded as Cardiff asserted their authority on the game.
Scott Sinclair, playing well wide on the right, appeared dangerous on the ball when he was able to get into the game, but it was Cardiff who appeared to be in control of the exchanges firing in more attempts on goal than the opposition.
Sinclair was substituted in the second half, while fellow newcomer Bowyer had a poor game.
Hameur Bouazza worked hard but their was no end product from his efforts.
Cardiff drafted in Chris Burke for his first appearance just before the break and the former Rangers player went very close to a story book debut early in the second half when he broke through only to have his close-range effort blocked in a combined operation by Radhi Jaidi and Liam Ridgewell.
On the hour, Burke did put his mark on the game. He collected a pass from Boothroyd and curled in a left footed cross from the right.
Jaidi headed out only to the waiting Ledley, who volleyed his shot into the top right-hand corner of the net for his fourth goal of the season.
The introduction of Seb Larsson generated more determination but these days Birmingham only appear to pull up their socks after going in arrears.
They obtained their last-ditch equaliser when a left-wing cross was headed by Cardiff's Steve McPhail into the path of the unmarked Bowyer to lash his shot past Peter Enckelman.