A brace from Watford striker Chris Iwelumo was enough to defeat Leeds and extend the Hornets' undefeated run to seven matches.
The 33-year-old put his side ahead on five minutes, placing Troy Deeney's through-ball past Andy Lonergan.
He then added a decisive second late on, tapping in Deeney's blocked shot.
Leeds defender Paul Connolly picked up a second yellow card in injury-time as United failed to win for the fourth successive match at Elland Road.
Iwelumo had only scored once for Watford prior to the match, but he wasted no time doubling his account - finishing off a simple chance after Deeney had broken through the home defence.
Both goalkeepers were called upon frequently in the match, Lonergan twice denied Deeney as the half progressed while Tomasz Kuszczak reacted sharply to keep out Robert Snodgrass at the other end.
Kuszczak was in the action again early in the second-half, pulling off a superb double save to first block Alex Bruce's header then deny Snodgrass on the rebound.
Substitute Ramon Nunez then curled a shot wide as Leeds pressed for an equaliser.
But it was Watford who finished the match stronger, Deeney breaking free on the left and forcing a save from Lonergan.
And Iwelumo sealed victory when he met a loose ball on the half-volley to wrap up three points and move Watford into the top half for the first time this season.
Leeds manager Neil Warnock: "I think we are miles away from where we should be.
"I couldn't see us scoring in a brothel today. Watford are a streetwise team and we have been mugged in every department. We were so naive.
"It showed why I got the job. A major overhaul is needed and I don't think the 7-3 defeat against Forest was as bad as this performance."
Watford boss Sean Dyche: "Big Chris [Iwelumo] has been excellent all season.
"He has been questioned all his career so it is not a problem to him. When he is ready to deliver he is a real handful.
"I am more than happy with winning 2-0 at Leeds. It was a very good, thorough performance."
"There are some big clubs fighting for play-off places but we will see what comes."