Ryan Taylor was on target in each half as Wigan recorded a vital win in their survival bid and leave manager Steve Bruce’s former club teetering above the relegation zone.
Taylor lashed Antonio Valencia’s cross past Maik Taylor as the hosts took a richly deserved lead before City’s Damien Johnson was sent off just before half time for a lunge on Kevin Kilbane. Kilbane recovered to hit a shot against the post moments later.
After the break Taylor was on hand again to touch in from close range to seal the points.
The result sees Wigan leapfrog Reading and go eight points clear of the drop zone.
Birmingham remain in deep trouble, however, and just four points separates them from third-bottom Bolton.