Two goals from Matt Holland helped Charlton extend their unbeaten sequence to five matches, from which they have collected 13 points, as they moved up to seventh place in the Premiership with a 2-1 win.
Despite losing Birmingham remained in fourth place in the table.
Charlton's real hero was former Republic of Ireland keeper Dean Kiely who produced two stunning saves to deny Christophe Dugarry and Mikael Forssell a late equaliser.
Bruce said: "It was disappointing to concede two goals from set-pieces but on the other hand the effort and spirit was terrific and I felt overall we deserved to get something from the game.
"Their keeper produced two or three great saves at a time when we had five strikers on the pitch and were trying to save the game.
"We saw glimpses of why I rate Charlton so highly. That's our first home defeat in nine months and we don't like it but I know this squad is honest and will bounce back and now we've got a big game at Wolves on Saturday."