Andrew Crofts’s 73rd minute strike fired Albion to the first win of Oscar Garcia’s reign.
The Seagulls had dominated proceedings in the first half, with Leonardo Ulloa providing the main threat but it was a far more even contest after the break, which saw the Blues strike the woodwork twice.
However it was Albion who made the all important breakthrough late on through the recalled Crofts, to record their first win at Birmingham since 1989.
Scott Allan’s early free-kick warmed up the hands of Tomasz Kuszczak before an audacious chip from Kemy Agustien dropped safely wide.
Oscar’s side had started brightly and positively, and Will Buckley had the best opening of the first ten minutes but his half volley was straight at Darren Randolph.
Ulloa has flown out the blocks this season and once again within 20 minutes he nearly grabbed his third goal of the season. Buckley’s teasing cross from the left was met by the Argentinean but his downward header just lacked the power to get the better of Randolph, as the keeper pushed the ball away.
Moments later David Lopez's exquisite chipped through ball was taken down by the onside Ulloa and after showing nimble feet to round the last defender, he scooped his effort wide narrowly wide.
Albion were dominant and looking more like the attacking force Oscar has been demanding, and debutant Stephen Ward was next to threaten for the Seagulls; the Irishman’s drilled strike from 20 yards narrowly flying over.
A speculative 35-yard dipping volley from Allan was the best effort from the hosts just past the half hour but the Seagulls defence were looking solid.
There was a late chance for the Blues as Andy Shinnie broke into the Albion box, however a tame strike was comfortably held as the sides entered the break goalless.
It was Shinnie again who threatened just after the interval, thundering a strike off the crossbar, and within 90 seconds Kuszcak’s bar was shaking again; Lee Novak finding the woodwork with his bullet drive.
Albion hit back through a blocked effort from Crofts, before Ulloa smashed the rebound wide. The Seagulls came even closer when Agustien powered his way through the heart of the Blues defence, but Randolph beat the Dutchman’s low shot away.
Tom Adeyemi’s deflected strike had the home faithful on their feet, but the midfielder’s shot had dragged wide and rebounded off the advertising board.
It was the Albion fans who were next on their feet and for all the right reasons as Agustien played Crofts in, and the Welsh international arrowed a finish into the bottom corner to the delight of the travelling fans.
The Seagulls almost had breathing space with five minutes of normal time remaining. Substitute Jake Forster-Caskey’s corner was powered towards goal by former Blues defender Mathhew Upson, Randolph made the save and Crofts failed to double his tally as he blazed the rebound over.
There was a typical late rally from the hosts but after losing from three winning positions already this season, Albion were not to be denied.