The victory was founded on an exceptional first-half performance and two magnificent goals, although after the break the home side were forced to show their resilience as the Canaries came back strongly and so nearly snatched a point at the death.
After a quiet opening with both sides taking time to size each other up, Watford took the lead in stunning fashion after 13 minutes.
Clarke Carlisle delivered a measured 40-yard pass to Marlon King who displayed an exquisite first touch to both bring the ball under control and spin away from Craig Fleming before smashing an angled right-footed drive across Robert Green to net his sixth of the season.
But if that goal was good Watford's second after 25 minutes was even better.
Matthew Spring flicked the ball to King who led a counter attack at pace. King then fed Ashley Young to his right and the striker moved inside the right edge of the penalty area before unleashing a ferocious left-footed drive that beat Green at his near post - but such was the power of his shot the keeper had no chance of getting near it.
Watford's dominance was so nearly cemented by a third goal just before the interval when Jason Shackell totally misjudged a bouncing ball, letting in King whose shot beat Green but rebounded back into the grateful keeper's arms off the far post.
Nigel Worthington made two changes at the break and switched to a 4-3-3 formation and this resulted in his team seeing a lot more of the ball in the second half, although Watford looked like they were coping until the hour when Dean Marney let fly from 25 yards and the swerve of the ball meant keeper Ben Foster was only able to parry it back out into the direction of Kevin Lisbie and the on-loan striker made no mistake.
Watford still looked comfortable after that only for Norwich to stage a late onslaught.
First substitute Gary Doherty saw a downward header from a Marney corner bounce off the post then Marney stabbed a good shooting opportunity wide from the edge of the area and then deep in injury time Marney again went close with a looping header which Foster had to tip over.