Sean Dyche's Clarets ended a three-game winless streak but extended their unbeaten run at Turf Moor to three matches thanks to a debut goal from summer signing Jeff Hendrick and second-half addition from star defender Michael Keane.
The opening goal came late in the first half when club-record signing Hendrick, who arrived from Derby County on deadline day, got on the end of Steven Defour's corner from the right to head home at the back post.
It was Hendrick's first ever goal in the Premier League.
Burnley doubled their advantage over Walter Mazzarri's Hornets on 50 minutes when Defour, at the second attempt, swung in a cross from the left which centre-half Keane powered home with his head for his first English top flight goal.
The Clarets wanted blood and almost got a third to kill off proceedings only for Heurelho Gomes to beat away Defour's rifled effort from the edge of the area on the hour-mark.
Hornets skipper Deeney had another key chance to pull one back but slipped at the crucial moment when the goal was at his beck and call, which basically summed up the night for the Hertfordshire outfit.
In the end, Burnley came away with a deserved lot of three points with their second triumph of the season which sees them move up to 13th position on the Premier League table with seven points from six matches.
For Watford, it was their first defeat in three league games after winning two on the trot, prompting them to fall to 11th
2016/17 Premier League - season scores