Fraizer Campbell’s second-half tap-in separated the sides and left Leeds without a win over their bitter rivals since 1984.
United dominated the first half and made a strong start to the second with Michael Brown slicing a shot over the crossbar moments after the restart.
But Tommy Smith fired a far better chance wide at the other end after a neat through-ball from Kim Bo-Kyung and Cardiff began to come into the game for the first time.
They took the lead on 64 minutes as Fraizer Campbell – introduced from the bench two minutes earlier – turned in Craig Bellamy’s volley after a poor clearance from Leeds right-back Sam Byram.
United threw on new signing Habib Habibou for the final 17 minutes and they came close to snatching an equaliser when Tom Lees’ header forced David Marshall to punch the ball desperately off his goalline but City held on.
Leeds manager Neil Warnock claimed his side should have had two penalties and accused referee Mike Dean of being in a bad position when Cardiff captain Mark Hudson appeared to handle the ball.
“It is a cruel game sometimes. Everything about today was cruel,” he said.
“We missed open goals and the young lad (Byram) made a schoolboy error. I thought Mike Dean was brilliant but he didn’t see the handball, when we all appealed, because he was in a bad position and should have been in a better one.
“He had three or four bodies in the way. The linesman could have helped him out, but they don’t, do they. Then there was another handball in the 93rd minute that wasn’t given.
“Our two centre-halves were magnificent, we played some good stuff against the top-of-the-table team and were better than them, so it’s very frustrating that we got nothing.”
Leeds United: Kenny, Byram, Lees, Peltier, White, Barkley, Austin, Brown, Varney, McCormack, Diouf. Subs: Ashdown, Pearce, Green, Warnock, Tonge, Norris, Habibou.
Cardiff City: Marshall, Connolly, Hudson, Turner, Taylor, Conway, Whittingham, Gunnarsson, Bo-Kyung, Bellamy, Smith. Subs: McNaughton, Cowie, Noone, Mason, Helguson, Campbell, Lewis.
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