Odion Ighalo scored the opening goal of the game just 44 seconds into the second half before Craig Cathcart doubled the home side's lead shortly before the hour mark.
Jamaal Lascelles pulled one back for the visitors, but the defeat for Newcastle sees Steve McClaren's side remain in the relegation places while Watford move up to 10th.
Patrick van Aanholt handed Sunderland boss Sam Allardyce the first draw of his 16-game reign as his side fought back to deny Bournemouth victory.
The Black Cats turned in an awful first-half display, but were trailing only by Benik Afobe's 13th-minute goal when Dutch full-back Van Aanholt levelled in stoppage time before the break to set up a frenzied, but ultimately fruitless, second 45 minutes.
Aston Villa's mini revival continued at West Brom but they were denied a first-half penalty in a goalless draw that stretched their unbeaten run to five games in all competitions.
The Premier League's bottom club were unfortunate not to have a spot kick awarded by referee Robert Madley when Jordan Ayew was felled by Jonas Olsson near the byline midway through the first 45 minutes.
In a game of few opportunities, it proved crucial as the Baggies claimed a share of the spoils despite offering little attacking threat at The Hawthorns.