Watford were unable to make the most of their attacking opportunities as Yeovil Town edged in front on the stroke of half time.
The Hornets started the brighter of the two sides and almost broke the deadlock on 16 minutes when forward Fernando Forestieri dragged his 20-yard effort narrowly wide of Wayne Hennessey's post.
Yeovil continued to soak up pressure in the early stages and Marco Cassetti went close to an opener when the defender met Troy Deeney's cross, but saw his effort blocked by Yeovil defender Liam Davis.
The home side were punished for their missed chances after Davis's cross was met at the far post by Byron Webster, who gave the Somerset club the lead against the run of play.
Watford are hoping to climb closer to the playoff positions in the Championship with a win, while Yeovil are currently two points adrift at the foot of the division.
Chris O'Keefe
