Birmingham carved out the vital win which as almost certainly assured their Premiership survival.
Bryan Hughes, who has been out of favour for most of the season after playing a key role in Birmingham's promotion last season, notched the important first goal two minutes before half time.
Frenchman Christophe Dugarry obtained the second in the 61st and it was a milestone as it was his first since joining Birmingham earlier in the year.
Sunderland's miserable day was completed when Marcus Stewart was sent off in the 86th minute for a vicious tackle on substitute Stern John.
Sunderland, fighting for their lives, attempted to grab an early lead but were thwarted by a determined Birmingham side fully aware of the need to acquire a victory to take them out of the relegation dog-fight.
But the end result was inevitable as Birmingham always had the edge despite Sunderland producing plenty of pleasing play.
Kevin Phillips and Marcus Stewart were both prominent in the early exchanges but Birmingham held firm to keep the Black Cats at bay.
Birmingham created the better goal opportunities and a big disappointment was the form of Dugarry.
The Frenchman was seeking his elusive first goal but he carelessly wasted a couple of good opportunities.
The first was a weak effort from a Paul Devlin right-wing cross and the second was a similarly weak header following a left wing corner by Stan Lazaridis.
Sunderland's best opportunity came from a square pass from Stewart into the path of Sean Thornton but the blond headed striker stumbled and wasted a clear opening.
It subsequently proved to be a costly miss as Birmingham took a vital 43rd minute lead when forgotten hero, Hughes, calmly lobbed the bal high over the head of debut goalkeeper, Mart Poom, and into the roof of the net.
Sunderland's fate was sealed in the 61st minute when Dugarry headed home his first goal for Birmingham from close range.