Bruce had gone in to the game on the back of successive home defeats and having seen his side collect just one point and one goal from their opening three matches of the season.
But the return of England international striker Heskey, who missed the last two games with a hip injury, proved to be just the tonic that Bruce and Birmingham needed.
Albion had their own two-goal hero in Blues old-boy Geoff Horsfield, who took his tally to four in two starts this season. But his heroics proved to be in vain as Albion slipped to a second successive defeat.
Having leaked four goals at Champions Chelsea in midweek, Albion were torn apart in the air as they struggled to come to terms with the power of Heskey.
Heskey sparked a flurry of four goals in the space of 22 first-half minutes when he headed City in front. Jamie Clapham fired in a left-wing cross after being picked out by Nicky Butt and Heskey completed the smart three-man move by powering home his header from six yards.
But the visitors barely had time to celebrate their advantage before Horsfield predictably dragged Albion back on to level terms.
Birmingham failed to deal with a corner from another City old-boy, debutant Darren Carter, and when the ball eventually found its way to Horsfield at the far post he drilled his shot past goalkeeper Maik Taylor.
Albion enjoyed their best spell of the half after Horsfield's equaliser but skipper Kevin Campbell wasted two golden chances - heading against the bar and shooting wide.
Birmingham proved to be far more clinical in attack and Albion were again undone in the air when Jiri Jarosik headed home a free-kick from Jermaine Pennant to regain the lead in the 26th minute.
It was a setback Albion struggled to get to overcome and their problems intensified seven minutes later when Heskey grabbed his second.
Once again, Pennant was the provider, collecting a pass from Mario Melchiot and delivering a perfectly placed right-wing cross that Heskey headed beyond Chris Kirkland.
It should have proved to be the end of Albion's challenge but Horsfield was on a one-man mission to salvage something from the game.
He gave Albion hope 19 minutes into the second-half when he capitalised on a shocking piece of defending by Damien Johnson.
Nathan Ellington's misplaced header flew straight to Johnson but his attempted clearance went back towards goal and to the feet of Horsfield, who bundled the ball beyond Taylor.
Horsfield then wasted a chance to rescue a point for Albion, and help himself to a hat-trick, 15 minutes from time. Ellington's long cross was turned back across the face of goal by Zoltan Gera, but the burly frontman was unable to get his far-post header on target.
Man of the Match: Emile Heskey
The England striker was the difference between the two teams. Albion simply had no answer to the aerial power of the former Liverpool marksman, who underlined his value to Birmingham with two smartly taken goals.