Demarai Gray's goal has given Birmingham City a 1-0 half-time lead at Elland Road.
Leeds had the majority of the ball but failed to make their possession count and were punished when Gray smashed home from 10 yards out, despite complaints by Liam Cooper that there was a foul by Clayton Donaldson in the build-up to the goal.
The 21-year-old had the best chance of the opening exchanges, but the winger dragged his shot wide after finding space inside the hosts' penalty area.
Debutant winger Will Buckley, signed on loan from Sunderland in midweek, had the best chance for Leeds as he forced Tomasz Kuszczak into a save with a difficult volley.
Stuart Dallas almost found an equaliser, but was thwarted by fantastic stop from Kuszczak.
Leeds are without a league win in seven months at Elland Road.
