A player nicknamed 'French Franc' by Middlesbrough fans was the goalscoring hero in an action-packed game that saw Steve McClaren's side climb to sixth place in the Premiership table.
Franck Queudrue hit a superb free-kick in the 28th minute to maintain Middlesbrough's impressive start to the season.
The 20-yard effort flew into the roof of the net past a bemused Nico Vaesen.
The victory maintained Middlesbrough's unbeaten home record this season although promoted Birmingham made them fight all the way for the three points.
The Blues lacked a cutting edge to their attacks but Middlesbrough fans were relieved at the final whistle after an exciting finale.
MIddlesbrough were without skipper Gareth Southgate and midfielder George Boateng so they gave a debut in defence to Tony Vidmar who arrived at the Riverside Stadium after being released by Rangers at the end of last season.
Croatian international Alen Boksic had a chance to relieve the tension for Middlesbrough fans with a goal shortly after his introduction as a first-half substitute.
The former Lazio player shot across the face of goal after an excellent pass from Massimo Maccarone.
Birmingham manager Steve Bruce was disappointed after the match. "I thought we deserved something from the game," he said.
"It's taken a marvellous goal to beat us. All credit to my side.
"I think you could see why we've already taken a few points in the Premiership. Neither side played particularly well in the first half but we gave it a real go after the interval.
"It's terribly disappointing not to have got something out of the game. There wasn't a bad tackle in the game but there were seven bookings. That will hurt when future suspensions start to kick in."