Cardiff leaped above Birmingham at the top of the Championship with a rampant show in front of a near sell-out 20,109 crowd at Ninian Park.
Cardiff seized control with a dominant first-half display
Michael Chopra starred in a storming first half, Joe Ledley opening the scoring on 12 minutes by burying a clinical left-foot shot from 12 yards.
The Blues rallied after the break, sub Cameron Jerome blowing a good chance.
But a poor defensive clearance fell to Steven Thompson who fed Paul Parry, the winger firing a decisive right-footer.
The win took the Bluebirds to the top of the second tier for the first time since March 1971 - when they were knocked off their perch by Birmingham.
Cardiff manager Dave Jones:
"We started like a house on fire after taking a bit of flak following Tuesday's defeat to Barnet.
"We will get better and we will get stronger, but in the last few weeks we have matched the top two teams in this division in every department and we didn't freeze in front of a huge home crowd.
"The noise was electric and the crowd deserved the cheers as much as the team at the end.
"In the past as a manager I have had seasons when we didn't have a win in the first seven games yet still went up.
"I've also had seasons where we started well but didn't win a thing so we'll keep everyone's feet on the ground and make preparation the key."
Birmingham manager Steve Bruce:
"The simple fact is that we were just not good enough particularly in the first half.
"You cannot expect to come to a place like Cardiff, play poorly and get something from the game.
"I spoke to Bryan Robson and he told me that playing Cardiff has been West Brom's toughest game of the season so I knew exactly what to expect.
"I am just disappointed that only three or four of my players played to their full potential. We have invested heavily in improving our goal ratio but you cannot afford to miss chances like we did today.
"Ninian Park is a fantastic place to play, there are not many left like it in the league but many of my players are used to the Premiership and World Cups so they should not have been affected by the atmosphere or surroundings."
Cardiff: Alexander, Gilbert, Loovens, Johnson, McNaughton, Parry, McPhail, Scimeca, Ledley, Thompson (Campbell 89), Chopra.
Subs Not Used: Flood, Glombard, Kamara, Gunter.
Goals: Ledley 12, Parry 75.
Birmingham: Doyle, Kelly (Larsson 58), N'Gotty, Jaidi, Sadler, Johnson, Nafti, Dunn, McSheffrey, Bendtner, Campbell (Jerome 58).
Subs Not Used: Legzdins, Forssell, Tebily.
Booked: N'Gotty, Johnson.
Ref: P Crossley (Kent).