Raheem Sterling headed the champions in front on four minutes when he converted Phil Foden’s cross from close range.
Sterling and Jack Grealish each drew saves from Daniel Bachmann before a dominant City doubled their lead on 31 minutes.
Ilkay Gundogan’s initial effort was blocked but the ball fell for Bernardo, who skilfully found the net from a narrow angle.
City made it 3-0 on 63 minutes when Bernardo brilliantly curled in his second.
Cucho Hernandez pulled a goal back for Watford on 74 minutes, converting at the second attempt.
Soccer Football – Premier League – Watford v Manchester City – Vicarage Road, Watford, Britain – December 4, 2021 Manchester City’s Bernardo Silva celebrates scoring their third goal REUTERS/David Klein EDITORIAL USE ONLY. No use with unauthorized audio, video, data, fixture lists, club/league logos or ‘live’ services. Online in-match use limited to 75 images, no video emulation. No use in betting, games or single club /league/player publications. Please contact your account representative for further details.
Watford threatened again when Joshua King fired wide, but a third straight defeat leaves them 17th on 13 points, three above the bottom three.
City leapfrog Chelsea and Liverpool on 35 points, one clear of the Reds.
Watford: 10 Dec v Brentford (A)
Man City: 11 Dec v Wolves (H)
Referee: Simon Hooper. Assistants: Adrian Holmes, Darren Cann. Fourth official: Rob Jones. VAR: John Brooks. Assistant VAR: Sian Massey-Ellis.