Chances were at a premium throughout, although Leeds' Rob Hulse really should have made the breakthrough midway through the first half when he was picked out unmarked in the area, but saw his low shot amazingly strike the inside of both posts before it was cleared.
Both sides made chances to win the game, with Robbie Blake replacing the injured Richard Cresswell for the visitors, while Watford boss Adrian Boothroyd was able to select skipper Gavin Mahon and former United midfielder Matt Spring in the centre of midfield for the first time.
All 22 players on view, plus the substitutes, put in plenty of honest endeavour, but the teams cancelled each other out as the game progressed.
After a quiet opening to the match Hulse spurned his golden opportunity after 25 minutes.
Former Scotland international defender Malky Mackay slipped as he tried to shepherd the ball over his own goal line and Blake nipped in and picked out Hulse.
His low effort first struck the inside of Watford keeper Ben Foster's left hand upright and rolled across the goal line before hitting the inside of the other post, and incredibly the ball still didn't cross the line giving Lloyd Doyley the opportunity to clear.
The only other chance of note in the first half came in injury-time, when Foster did well to get behind Blake's well-struck 25-yard free-kick.
Chances continued to be in short supply after the interval, although both teams made attacking substitutions in an attempt to break the deadlock.
One of the replacements, Danny Pugh, was not far wide with a left-footed half-volley for the visitors, while at the other end Doyley forced Neil Sullivan into a smart save at his near post.
The inevitable outcome was confirmed when Pugh struck a tame half-volley at Foster following an enterprising break down the right flank by Frazer Richardson.
Man of the Match: Sean Gregan
Gregan was the outstanding performer in the game, dealing with Watford's aerial attempts with relative comfort and helping the Leeds defence to stay composed as Watford swung in a number of dangerous crosses and set-pieces.