Clinton Morrison opened the scoring for the hosts on 10 minutes and Darren Anderton doubled their advantage nine minutes later.
However, a Michael Dowson brace in the final five minutes of the first half sent the sides in 2-2 at the break.
Just two minutes into the second period and Birmingham winger Mat Birley scored what proved to be the winner for the home side.
Birmingham: Doyle, Blake, Alsop, Howell, A Hall, Kilkenny, Clemence, Anderton, Birley, Barrowman, Morrison. Subs: Legzdins, M Hall, Cottrill, Till, Wright.
Sunderland: Carson, Taylor, D. Smith, Christensen, Hartley, Martin, Davison, Richardson, Dowson, Allan, Dennehy. Subs: Chapman, Backhouse, Weir, Smith, Connolly.