Super Eagles striker Odion Ighalo’s early goal gave Watford their third successive win, leaving Sunderland stuck in the bottom of the table.
The Nigerian international benefited from Allan Nyom’s low cross at the near post after getting ahead of Black Cats defender Sebastian Coates to divert the ball past Costel Pantilimon for the opener and eventual winner.
Sunderland tried to find a response but despite dominating the second half with Jermain Defoe and Jack Rodwell forcing good saves from Gomes, the Hornets hung on for a victory that moves them up to seventh on the log after 16 games.
Sunderland boss Sam Allardyce spoke before the game about the importance of keeping Ighalo and his strike partner Troy Deeney quiet, but succeeded for only four minutes as Ighalo went on to score his 10th goal of the season and his 26th in 2015 – more than any other player in the top four tiers of English football.
The Nigerian remained a constant threat in the Black Cats defence soon afterwards, with Jose Manuel Jurado firing against the post after Ighalo had wriggled past Sebastian Coates on the right.
Ighalo could have added to his tally in the second half, twice wasting shooting chances after Watford launched quick counter-attacks.