Story of the match
Cardiff boss Steve Morison made two changes to the side that lost 2-1 against Reading last week, with Perry Ng and Jaden Philogene-Bidace coming into the starting eleven to replace Curtis Nelson and Sheyi Ojo.
John Eustace made one change from the Birmingham side that beat Huddersfield Town 2-1 last Friday, with youngster Alfie Chang handed a first league start replacing Ryan Woods, who is strongly linked with a move away from St. Andrews.
The home side applied all the early pressure, dominating possession and forcing Blues keeper John Ruddy into an early double save, denying Romaine Sawyers' low shot before clawing away the rebound from Max Watters.
The Bluebirds secured an early lead, with Callum O'Dowda slipping past Przemysław Płacheta on the left before fizzing a low cross into an unmarked Philogene-Bidace, with the Aston Villa loanee converting from point-blank range.
Cardiff certainly deserved their lead and looked more comfortable in the contest, but Birmingham came close to a shock equaliser as Troy Deeney played a delicate flicked ball into the path on an onrushing Scott Hogan, who was denied by an excellent last-ditch challenge from a recovering Jamilu Collins.
Cardiff came agonizingly close to a second goal, as Birmingham midfielder Juninho Bacuna was robbed of possession by O'Dowda who spotted Watters baring down on goal, but the striker was denied by a brave stop from Ruddy who ventured off his line to deny Watters his first league goal of the season.
The second-half commenced and Cardiff continued in the same manor, with O'Dowda stinging the gloves of Ruddy from close range.
Ruddy was certainly responsible for keeping his side in the contest, with Birmingham having a strong penalty appeal turned down minutes later, as Hogan was clipped from behind by a chasing Cédric Kipré, but referee Darren Bond seemed to not spot the contact and booked Hogan for his protests.
Cardiff substitute Kion Etete had a couple of near misses, but the Bluebirds managed to deal with the limited Birmingham threat to gain victory.
Player of the match - Callum O'Dowda
The Irishman was the main man for Cardiff this afternoon, getting the better of Płacheta on multiple occasions, especially for the goal. O'Dowda was physical in his game and looks to be a dependable figure going forward for Steve Morison's side.