Going into the contest with just one win in their last five, Simon Grayson's men could feel the chasing pack breathing down their necks as they clung on to sixth place, and it looked as though they had bought themselves some breathing space when substitute Luciano Becchio headed home his 20th of the season to make it 1-0 with 19 minutes left.
But, as has often been the case for the Whites this season, where their attack has excelled their defence has failed and so it proved again as Lee Hodson nipped in unmarked to level for Watford seven minutes later.
Danny Graham then outmuscled Andy O'Brien to play in Andy Weimann for what looked to be an 87th-minute winner for the visitors.
But Leeds quickly went down the other end and, after winning a corner, were left celebrating a draw and a return to a two-point margin over their rivals after Troy Deeney turned Barry Bannan's corner into his own goal.
Watford went into the game unchanged from the side that drew 2-2 with Norwich on Tuesday, while Leeds made four changes following the 2-1 loss at Derby, with Becchio amongst the casualties.
Eager to erase the memories of the Derby defeat, Leeds stated brightly with a Max Gradel overhead kick creeping wide, before Watford got on top.
Graham, the Championship's leading scorer, bore down on goal after a slip by Leigh Bromby and, after skipping inside O'Brien, should have done better than firing at Kasper Schmeichel.
Both Bromby and O'Brien were struggling to deal with Graham's physicality, and moments later O'Brien forced Schmeichel to tear across his goal and hack a overhit backpass to safety.
Deeney, Graham's strike partner, then beat Bromby to a bouncing ball and set Graham free, but his cross evaded everyone, especially Marvin Sordell who would have scored had he been alert enough.
Back came Leeds, though, and Jonny Howson had a shot blocked by John Eustace after good link-up play between Robert Snodgrass and Eric Lichaj, before Snodgrass danced his way into the box and crossed for Gradel who hit the bar from two yards out.
O'Brien's outstretched leg sent a Danny Drinkwater shot flying just wide of his own goal after the interval, before Grayson called on Becchio with 35 minutes remaining as he became increasingly desperate for a breakthrough.
Becchio's impact was almost immediate as he flicked on a long Lichaj throw for Bradley Johnson to head narrowly wide. Gradel then wasted a golden chance as he drove at Scott Loach rather than squaring to Snodgrass after breaking clear.
Watford then hit the woodwork, with Don Cowie's header catching Schmeichel flatfooted after Bromby allowed Graham to work in a cross, while at the other end Davide Somma could not quite get on the end of a Johnson header across goal.
Becchio then opened the scoring for Leeds, planting an unstoppable ahead beyond Loach from three yards out after a fizzing ball in from Bannan.
The former Barcelona B striker should have made it two shortly after, blazing over after being played in by Johnson, before Watford leveled with 12 minutes remaining.
An innocuous-looking cross from Cowie drifted its way into Leeds' box and Hodson nipped in behind Bromby to head home.
Becchio was then substituted himself after getting injured in a scramble that followed a Johnson header being cleared off the line, before Watford stunned Elland Road into silence when Graham won a 30-70 ball agaisnt O'Brien and squared for the waiting Weimann who drove in.
There was still time for further drama, though, with Deeney bundling another precise Bannan cross into his own goal.