Willo Flood struck an 83rd-minute winner at Elland Road to send Cardiff joint top of the Championship.
Flood converted Michael Chopra's cross into the penalty area from close range as Cardiff built some late pressure.
Leeds had earlier gone close as Eirik Bakke and David Healy forced fine saves from Cardiff goalkeeper Neil Alexander.
Cardiff captain Darren Purse was sent off for violent conduct on 90 minutes and Shaun Derry's injury-time header forced Alexander into action again.
Leeds manager Kevin Blackwell:
"At the moment things aren't dropping for us.
"We had all the best chances in the game and dominated for long spells. But that's life, isn't it?"
Cardiff manager Dave Jones:
"We played very well and thoroughly deserved the victory.
"It's not a bad start but there's a long way to go.
"If the players are prepared to listen and learn then it bears well for the
future of the football club."
Leeds: Warner, Kelly, Butler, Kilgallon, Crainey, Westlake, Stone (Bakke 32), Derry, Lewis (Carole 85), Healy, Blake (Beckford 68).
Subs Not Used: Gregan, Richardson.
Booked: Bakke, Healy, Derry.
Cardiff: Alexander, McNaughton (Johnson 87), Purse, Loovens, Ledley, Kamara (Flood 68), Scimeca, McPhail, Parry, Chopra (Blake 90), Thompson.
Subs Not Used: Glombard, Campbell.
Sent Off: Purse (90).
Goals: Flood 83.
Ref: N Miller (Co Durham).