Newly-promoted Norwich moved another step closer to clinching the Division One title with goals from Damien Francis and Leon McKenzie.
Francis opened the scoring when he latched on to McKenzie's pass to steer the ball past Alec Chamberlain.
The Canaries doubled their advantage after the break when McKenzie deflected in Kevin Cooper's free-kick.
Debutant Dominic Blizzard set up a tense finale with a late header that ended Norwich's 401-minute shut-out.
The victory means Norwich remain two points clear of West Bromwich Albion in the race for first place with three games remaining.
And it also saw Nigel Worthington's team claim their sixth successive win - the first time the Norfolk outfit have managed such a feat since 1986.
Norwich's goals were a deserved reward for their dominace but they were forced to work hard for the points thereafter by a determined Watford side.
McKenzie went close early on, and having set up Francis for the opener, got in on the act with his eighth goal in 15 games when he got in the way of a free-kick awarded for Chamberlain picking up a back pass.
That sense of injustice stung the Hornets into a strong spell when Sean Dyche, who went close with a first-half header, nearly cut the arrears only to see his shot hit the woodwork.
Chamberlain made amends for his earlier error to deny Craig Fleming before Blizzard finally gave the home support something to cheer.
Darren Huckerby could have made the game safe with a third for Norwich before Iwan Roberts saw an effort, from his first touch, saved by Chamberlain in an exciting finish.
Watford: Chamberlain, Baird, Dyche, Gayle, Mayo, Devlin, Hyde, Mahon, Cook, Bouazza, Dyer. Subs: Ardley, Doyley, Fitzgerald, Pidgeley, Blizzard.
Norwich: Green, Edworthy, Mackay, Fleming, Drury, Cooper, Francis, Holt, Huckerby, Svensson, McKenzie. Subs: Mulryne, Roberts, Brennan, Crichton, McVeigh.
Referee: M Fletcher (Worcestershire).