DAVID Dunn came back to haunt his former club with a goal in each half to stretch their unbeaten home league record to seven.
In a game of few goalmouth chances, the former Birmingham man, who rejoined his boyhood club three years ago, grabbed a stunning opener after just five minutes.
Then harshly had a second ruled out for a supposed foul from Michel Salgado.
But nerves were jangling from the home fans when James McFadden's smart free-kick evened up proceedings after 55 minutes, but there was to be no denying Dunn who arrived at the near post on 67 minutes to head home El-Hadji Diouf's corner kick.
Dunn had to leave the pitch prematurely after Barry Ferguson kicked out at the midfielder, taken the shine off another three-point haul at Ewood Park.
It came as little surprise that Sam Allardyce chose to stick with the same starting eleven that did so well to claim a point against Chelsea on Sunday.
Despite Ryan Nelsen being fit enough to be in the squad, he had to settle for a place on the substitutes bench as Phil Jones retained his place.
Keeping the same eleven paid dividends just five minutes into the game as Rovers took the lead. Chris Samba's long ball forward saw Niko Kalinić give Birmingham defender Roger Johnson all manner of problems that he could only head the ball into the path of the onrushing David Dunn who controlled the ball on his chest before lashing a 20-yard effort that flew past Joe Hart into the corner of the net.
It just had to be Dunn scoring against his former club.
Rovers were thankful for the alertness of Jason Brown in goal as the visitors looked to hit back quickly. Craig Gardner's short free-kick finding James McFadden who's shot from the corner of the area took a deflection, but that didn't stop Brown diving to his right to push the ball aside.
Sunday's man of the match Phil Jones was on the end of an errant elbow by Birmingham striker Cameron Jerome, but it barely merited a talking to by referee Mark Clattenburg.
Birmingham threatened but without ever causing undue problems in the Rovers area. Indeed it was Rovers who had the ball in the back of the net again but Dunn's effort was ruled out after Michel Salgado had pulled down Lee Bowyer as he played the pass.
An El-Hadji Diouf cross saw Niko Kalinić and Morten Gamst Pedersen cause Joe Hart problems at his near post, but Ridgewell got back in the nip of time to clear behind.
The second half was slow to get going with both sides cancelling each other out in what was slowly descending into a midfield battle.
But it was from one of those midfield battles that the visitors got back on level terms as one free-kick lead to another and James McFadden curled a superb 20-yard effort around the wall and past a flat footed Jason Brown.
At that point Rovers looked leggy, their efforts in gaining a point against Chelsea on Sunday appearing to catch up on them.
But if Rovers were to have an uncomfortable end to the game then David Dunn had other ideas as just ten minutes later he'd headed the home side back in front.
It came from a corner kick that referee Mark Clattenburg deliberated long and hard before giving it in Rovers' favour. El-Hadji Diouf stepped up and sent the ball to the near post where David Dunn scored with a rare header.
That was Diouf's last involvement as Junior Hoilett came on to replace and he immediately caused the Birmingham back line problems with his trickery and pace, one run seeing a shot at goal deflect wide.
Continuing to look for more goals, Chris Samba's powerful header from a Pedersen corner almost flicked in off Jason Roberts, but Joe Hart claimed.
The visitors threw on Christian Benitez and Kevin Phillips in an attempt to rescue a late point, but Rovers held on with comparative ease despite playing five additional minutes at the end of the ninety.
The final whistle signalled nine home wins and up a place in the table to 11th, and puts Rovers in good heart ahead of a certain Sunday showdown.
ROVERS: Brown, Salgado, Samba (c), Jones, Olsson, Pedersen, Andrews, Nzonzi, Dioufs (sub Hoilett 69 mins), Dunn (sub Emerton 88 mins), Kalinić (sub Roberts 46 mins).
Subs not used: Bunn (GK), Nelsen, Di Santo, Chimbonda.
BIRMINGHAM: Hart, Carr (c), Bowyer, Ridgewell, Jerome (sub Benitez 73 mins), Ferguson, Johnson, Dann, McFadden, Fahey (sub Phillips 79 mins), Gardner (sub Larsson 73 mins).
Subs not used: Taylor (c), Michel, Parnaby, Vignal.
Booked: Dunn, Andrews (Rovers), Carr (Birmingham)