Goals by David Bentley and Benni McCarthy secured victory for Blackburn despite a spirited Birmingham effort.
Bentley opened the scoring with a sublime piece of skill
The lively Bentley struck in the 15th minute, swivelling inside the box and firing past Maik Taylor's left hand.
Birmingham thought they had levelled but Gary McSheffrey was judged offside, before McCarthy stroked home a penalty after Roque Santa Cruz was fouled.
Cameron Jerome pulled one back with a rocket into the top corner but the visitors could not find an equaliser.
Birmingham will feel the match hinged on the moment when McSheffrey's stabbed effort during a goalmouth scramble was harshly ruled out, as he appeared to be level with the last defender.
The Blues were two down rather than level within a minute as Blackburn broke immediately to the other end and were awarded a penalty for Johan Djourou's challenge on Santa Cruz, McCarthy making no mistake from the spot.
Bentley had signalled his intent with a 25-yard shot in the first minute, and he went close nine minutes later with a lovely control and volley narrowly wide of Taylor's right-hand post from the edge of the area.
Birmingham had the best of the early exchanges with three corners inside 11 minutes, but went behind to a flowing Blackburn move.
Following good work down the right wing, David Dunn crossed low inside the box to Bentley, who turned and fired lowed through Stephen Kelly's legs inside the near post.
Jerome had a chance to equalise when he beat Blackburn's offside trap to latch onto a through ball but he fired wide from the corner of the six-yard box.
Santa Cruz, Stephen Warnock and Christopher Samba all had chances for the hosts in an entertaining first half but they went to the interval with a 1-0 lead.
It was almost 2-0 straight from the restart, but Frank Queudrue managed to block Bentley's side-foot effort from inside the six-yard box.
Birmingham pressed after going two down and were finally rewarded when Jerome latched onto to a header and blasted home after Blackburn failed to clear their lines.
The Blues looked for an equaliser but it was man-of-the-match Bentley, again, who went close when he shot into the side netting from 15 yards.
Blackburn goalkeeper Brad Friedel had to be alert to palm over Olivier Kapo's close-range header in injury time.
Blackburn manager Mark Hughes:
"I thought we were a little bit off the pace in the first half, perhaps because of Thursday's efforts in the Uefa Cup.
"In the second half we were more dynamic, and when Benni McCarthy came on he looked very sharp.
"There were lots of positives. I've got a good group of players and we'll need them all during the season."
Birmingham manager Steve Bruce:
"It is a bit frustrating; we deserved to get something out of the game. Today was there for the taking.
"The big turning point in the match was the disallowed goal. They put the linesman under enormous pressure here, and he put the flag up.
"There should to be daylight between the attacker and the last defender. Thirty seconds later it's over."
Blackburn: Friedel, Emerton, Samba, Ooijer, Warnock, Savage (Mokoena 57), Kerimoglu (Derbyshire 56), Bentley, Dunn (McCarthy 46), Pedersen, Santa Cruz.
Subs Not Used: Brown, Khizanishvili.
Booked: Kerimoglu, Warnock, Bentley
Goals: Bentley 15, McCarthy 56 pen
Birmingham: Maik Taylor, Kelly, Djourou, Ridgewell, Queudrue, Larsson, Muamba (Palacios 62), Nafti (Danns 72), McSheffrey (O'Connor 62), Jerome, Kapo.
Subs Not Used: Kingson, Schmitz.
Goals: Jerome 68
Ref: Mark Clattenburg (Tyne & Wear)