Jerome even missed an open goal only a minute before grabbing Birmingham's second. He also notched Birmingham's third.
Fabrice Muamba notched a fourth goal, but it was all to no avail as the Fulham and Reading results became known.
Birmingham, however, could have no complaints. They have contributed to their own downfall with some poor home performances this season and return to the Championship after only one season in the top-flight.
Blackburn were under strong first-half pressure but dominated most of the second half after getting back into the game with Pedersen's equaliser.
Birmingham suffered a blow when Scotland international James McFadden was forced to drop out of the side with a knee injury.
His replacement, Mauro Zarate, quickly impressed with some tricky footwork, but his finishing left a great deal to be desired as he hammered a shot well wide to his own frustration.
As to be expected, Birmingham played at a frantic pace despite the humid conditions but Blackburn held firm as the home side seemingly ran out of attacking ideas.
The closest Birmingham came to breaking the stalemate occurred in the 28th minute when a glancing header from Olivier Kapo went wide of the far post following a cross from Seb Larsson.
Birmingham then took the lead completely out of the blue as Zarate played a free-kick back to Murphy and the former Hibs player advanced unchecked.
As no challenge materialised, he tried a hopeful shot from 25 yards which completely deceived Brad Friedel and scurried into the far corner of the net.
Birmingham had a let-off when goalkeeper Maik Taylor was stranded off his line and, just as Jason Roberts closed in to convert Brett Emerton's cross, Stephen Kelly made a desperate clearance on the near post.
But three minutes into the second half, Blackburn were on level terms following another massive mix-up in Birmingham's defence.
Liam Ridgewell made the original mistake to let in Roberts. Taylor bravely saved the first attempt but the ball rebounded to Roque Santa Cruz, who slipped the ball into the path of Pedersen to equalise.
Jerome took over from Mikael Forssell and Murphy set him up with a golden chance only for the former Cardiff player to lift the ball over the bar.
But he made amends when he scored on the volley in the 73rd minute to convert a cross from Larsson.
Jerome notched his 89th minute goal when he collected a Gary McSheffrey cross to notch a simple third goal on the volley with Muamba heading home a cross two minutes from time.