Bruce, whose first return to City since his acrimonious departure almost two years ago came on the day Carson Yeung's new regime was launched in earnest, could only look on as his side fell 2-0 behind with 48 minutes gone.
Defender Liam Ridgewell's opener on 37, bundled home from Sebastian Larsson's free-kick, and midfielder James McFadden classy low strike on 48 doubled City's league tally at home this season and were ultimately enough to clinch the points, although only just.
Sunderland gave themselves a lifeline when Scott Dann put through his own goal with eight minutes remaining, but substitute Fraizer Campbell and leading scorer Darren Bent passed up late opportunities to wrestle back a point.
But that would have been harsh on the home side, who dominated much of what had gone before in front of a delighted crowd of 21,723 - following a rallying call from new chairman Vico Hui on the pitch before kick-off.
Bruce insisted in the run-up to his return that Sunderland's heroics against Manchester United and Liverpool in their last two matches, which yielded four excellent points, would count for nothing if they left St Andrew's empty-handed - and his caution proved well-founded.
His fears of an 'after the Lord Mayor's show' performance became depressing reality before the break as his side struggled to get out of their own half, let alone exert any real pressure on Joe Hart's goal.
It took the visitors 40 minutes to muster their first effort of note, and even then Andy Reid's left-footed effort flew well wide.
By contrast, Birmingham - who went into the game having won only twice in the league and with just six goals to their name to date - were by far the more enterprising and were well worth their half-time lead.
They created several opportunities, with McFadden and Cameron Jerome forcing regulation saves from goalkeeper Craig Gordon.
It took a last-ditch block from defender Michael Turner to stop
McFadden converting Christian Benitez's 27th-minute return pass.
Scotland international Gordon had to distinguish himself with a fine save from Benitez at his near post seconds later as Birmingham established a real momentum, and they got their noses
in front eight minutes before the break.
Ridgewell got the decisive touch to Sebastian Larsson's swinging free-kick to divert the ball into the net, although he looked to do so from an offside position.
Where the visitors got the benefit of the doubt in last weekend's infamous beachball-gate incident, they were on the receiving end this time around.
Benitez went close from long range once again with 44 minutes gone, and the Black Cats headed for the dressing room expecting a forthright assessment of their efforts from the manager.
But whatever he said fell on deaf ears, as City soon extended their lead.
Larsson's cross was slightly behind Jerome, but he cleverly flicked it into McFadden's path.
The Scot stepped inside wrong-footed full-back Phil Bardsley and steadied himself before passing the ball past Gordon and into the net - despite Turner's desperate attempt to clear off the line.
Sunderland's response was laboured in the extreme, with strikers Kenwyne Jones and Bent seeing little of the ball, and their woes might have increased with 64 minutes gone had Benitez's shot crept inside rather than outside the post after clipping Bardsley's heels.
Bruce decided enough was enough and with 68 minutes gone. He sent on Campbell, George McCartney and Bolo Zenden for Steed Malbranque, Jordan Henderson and captain Lorik Cana - but it was too little too late.
Sunderland stirred as the game entered the closing stages and got their reward with eight minutes left when Dann could only help Turner's glancing header into his own net.
Campbell might have snatched a point when he climbed to meet Reid's 84th-minute cross but headed high over, and Bent went even closer with an 89th-minute volley which shaved the post.
There was still time for Gordon to escape with a yellow card for handling outside his box, Benitez chasing down a long ball as the home crowd bayed for red. But the job was done.