A goal each from Dele Alli and Harry Kane was enough to secure Tottenham Hotpsur all three points.
The Lilywhites were far from at their best but still offered too much for the Watford outfit to deal with.
Javi Gracía's side have now gone seven games without a win as their season grinds to an end.
The victory regains Tottenham's five-point cushion on their London rivals Chelsea in the race for a top-four finish.
Dele opens the scoring
Without having caused Watford any trouble in the opening stages of the game, Alli put Spurs ahead after 16 minutes.
Kieran Trippier's cross was fumbled by Orestis Karnezis and the ball ended up at the feet of Dele who calmly slotted home.
A gift of a goal to give away by the visiting side after Spurs had struggled to get out of first gear.
The Lilywhites did not begin the game in their usual high tempo fashion but still managed to find a way through.
Dele's goal marked his tenth of the season in the Premier League.
Kane back on track
Kane doubled Tottenham's lead just minutes after the interval with a simple tap-in.
Moments after squandering a golden opportunity the English talisman found himself on the end of a Trippier cross with the goal gaping.
It was the worst possible start for Watford who had ended the half in such promising fashion.
However, Kane's goal brought his tally up to 27 Premier League goals for the season - just four behind Mohamed Salah in the race for the golden boot.
Watford unlucky to be behind
Tottenham looked dormant throughout the opening stages of the game and fortuitously found themselves in front.
Despite dominating the possession, Tottenham were unable to cause the Hornets any problems.
However, the opening goal seemed to spring life into the visitors as they quickly carved out a superb chance on Hugo Lloris's goal.
Andre Gray found himself one-on-one with the Spurs captain but forced a superb save from Lloris - who got down quickly to deny Gray.
As the game progressed it was Watford who began to grow into the game as the subdue Wembley atmosphere summed up the Spurs performance.
Lethargic and playing without any intent, Tottenham left themselves at serious risk of conceding an equaliser.
The Hornets pressed and on numerous occasions came close to levelling the proceedings.
Richarlison broke down the left side and stung the palms of Lloris but the home side prevailed.
Just before half-time, Abdoulaye Doucouré found himself in a race with Lloris for the ball in the middle of the Spurs half but it was the Spurs captain who came out on top.
Spurs would have been glad to hear the half-time whistle and should have felt fortunate to end the half leading.
Spurs prevail
The second-half was immediately lit up by a Harry Kane goal but quickly returned to the low tempo pace of the first 45.
Mauricio Pochettino seemingly demanded his side pressed the visitors at their usual tempo but found themselves of committing too many bodies in the Watford half at times.
Richarlison missed a golden opportunity to reduce Watford's two-goal deficit from just six-yards out.
Minutes later, Gerard Deulofeu put the ball in the Tottenham net after rounding Lloris but his celebrations were cut short as the goal was ruled out for offside.
Harry Kane believed he had doubled his tally for the night after he also put the ball beyond the goalkeeper.
However, the Englishman had the goal disallowed after finding himself a yard offside.
Despite some superb chances on goal neither team were able to convert and the game petered out to an end.