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.
Heading into Saturday's encounter, Quique Sanchez Flores claimed fatigue had contributed to his team's poor run, but the Watford manager made only one change with Juan Carlos Paredes coming in for Allan Nyom
Nordin Amrabat, the £6million signing from Malaga, was handed a place on the bench.
For the visitors, Lascelles was drafted into McLaren's starting XI while Henri Saivet was handed his full debut, and Rolando Aarons made his first league start of the season.
It was Aarons, operating as a left wing-back, who had the first opportunity of the game
The ball fell to the 20-year-old on the edge of the Watford area, but he steered his half volley just wide of Heurelho Gomes' left post.
Ahead of the game, Watford had failed to score in their last two matches while Newcastle had netted only five times on the road this season - the lowest of any team in the top seven tiers of English football
Unsurprisingly the first half saw few opportunities for either a side.
After 17 minutes Etienne Capoue seemed certain to score when Troy Deeney's effort was fumbled by Rob Elliot but the Newcastle keeper scrambled to his feet to block the Frenchman's follow-up strike
Midway through the first half Georginio Wijnaldum teed up Aleksandar Mitrovic, but his effort was saved by the legs of Gomes and the ball drifted out for a corner
That was as good as it got with referee Andre Marriner blowing his whistle on a rather dreary first half
The second period was a different story altogether, and just 44 seconds had gone when Capoue dinked a ball over the top of Newcastle's static defence and Ighalo had only Elliot to beat
The Nigerian made no mistake as he rounded the Magpies' stopper and side-footed home into an empty net
Replays suggested Ighalo, now with 14 goals to his name this term, may have been offside, but neither the home fans were not complaining
Watford were in command and moments after Valon Behrami was booked for being adjudged to have dived in the penalty area, the home side doubled their advantage
Newcastle failed to deal with a corner and the ball fell to Cathcart who fired home from close range shortly before the hour mark
A double substitution ensued for the visitors with Yoan Gouffran and Ayoze Perez replacing Aarons and Saivet
Moments after coming on, the latter found himself unmarked and six yards from goal, but his header - following a pinpoint cross by Moussa Sissoko - went high and wide
It did not look as though it would be Newcastle's afternoon, but suddenly they were handed a lifeline when Lascelles out-jumped Miguel Britos to head home Jonjo Shelvey's corner
Substitute Perez was then played through by Wijnaldum but fired his shot over
At the other end Ighalo twisted one way and the other before his fierce shot was well saved by Elliot
Newcastle pressed for an equaliser but it never came as Watford recorded their third victory over the Magpies this season
Source : PA
Source: PA