Middlesbrough 0-1 Leeds United
Leeds produced a resilient display to claim a fifth win in six games as league-leaders Middlesbrough missed out on the chance to go four points clear at the top of the Championship.
Alex Mowatt's deflected shot from the edge of the box gave the away side the lead in just the third minute.
And Scott Wootton hit the crossbar with a close-range header for United.
But Boro dominated for long periods and Leeds were indebted to keeper Marco Silvestri for a string of good saves.
The 23-year-old Italian was not the only key figure for Leeds, with new captain Sol Bamba producing a superb display in defence and a number of important of blocks to deny the home attack.
And Mowatt, who scored Leeds' only goal against Millwall a week ago, was again the match-winner - his shot finding the net after he was set up by Lewis Cook following a misplaced throw from home keeper Tomas Mejias.
However, despite taking the early lead, Leeds were on the back foot for much of the rest of the first half as Middlesbrough came back strong.
Aitor Karanka's team had not lost in the league since 20 December and were unbeaten at home since August, and they would have been level but for Silvestri, who produced superb saves to push away a Kike shot and block an effort from Jelle Vossen before fending away a long-range drive from Adam Clayton.
Leeds had chances to double their advantage, with Bamba heading wide from close range, Wootton's header hitting the bar and Rodolph Austin seeing a shot saved by Mejias following an incisive break.
But despite bringing on strikers Patrick Bamford and Lee Tomlin, and playing nine minutes of injury time - for a head injury to Vossen that left the home side with 10 men - Boro were unable to break through.
Middlesbrough manager Aitor Karanka:
"Today is the kind of day you cannot explain. We are frustrated because we have done everything to win this game and we haven't won it.
"I can't say anything bad about my players because they have done their best. We now have to think about Tuesday against Bolton.
"I thought the performance was very good. I don't know how many chances we had. However, we have an important game on Tuesday.
"The best thing is to play again on Tuesday, especially at home. This team always reacts very well after a defeat."
Leeds United head coach Neil Redfearn:
"Our recent run is very satisfying. But we have got to make sure we don't get carried away with ourselves.
"We are a young side and we have been through a lot of adversity. We are going to get better and better.
"Reaching the play-offs is a tall ask but while there are points to play for there is no reason not to aim as high as you can."