Three goals in 15 second half minutes saw Birmingham edge out the Owls 2-1 in the live TV clash on Saturday evening.
Substitute Gary Hooper opened the scoring for the visitors, who barely had time to enjoy the lead before the Blues hit back with a Clayton Donaldson penalty.
Then right at the end, Blues substitute Lukas Jutkiewicz claimed all three points, heading the winner with almost his first touch from the bench.
It was hard on Wednesday, who were largely in control from the outset and although Birmingham rallied in the second half, the Owls had the overall edge.
Three times they penetrated in the early exchanges alone, with Fernando Forestieri forcing a fine save from Adam Legzdins, who darted off his line to parry the striker’s shot to safety.
Then Barry Bannan attempted an audacious chip from distance that only just evaded Legzdins’ crossbar, before Almen Abdi’s header brushed the top of the net.
The remainder of the opening 45 unfolded in similar fashion, albeit the Blues did offer more as events unfolded.
Ex-Owl Jacques Maghoma had a half-hearted penalty appeal turned down and Donaldson spurned a good chance on the whistle of a half that Wednesday dominated.
Birmingham started brighter after the break and Maikel Kieftenbeld struck the outside of the post with an improvised effort on the angle.
The Blues made a double substitution on the hour to further up the tempo, while the Owls introduced Hooper, two-goal hero of the corresponding fixture last season.
And he was duly on target on 76 minutes. Steven Fletcher did exceptionally well to send Hooper through down the left of the penalty area and the hitman did the rest, finishing coolly past the despairing Legzdins.
But three minutes later, Birmingham were right back in it after Keiren Westwood brought down Donaldson in the box.
The referee pointed to the spot and Donaldson climbed off the floor to convert.
Both sides pressed for a winner and Atdhe Nuhiu almost got it in stoppage time, thumping a header against the crossbar.
But Birmingham went one better moments later as Maghoma crossed for Jutkiewicz to nod across Westwood and in.
Wednesday: Westwood, Palmer, Lees, Loovens, Reach, Wallace (Buckley 86), Lee, Bannan, Abdi (Hooper 65), Forestieri, Fletcher (78)