© PA Photos
The contest started in cagey fashion, with the first chance coming in the 15th minute when Troy Deeney found space inside the area but the forward failed to hit the target with his effort.
Deeney quickly atoned for his mistake five minutes later as he outpaced two Forest defenders before crossing for Vydra to slot the ball into the back of the net.
Deeney managed to add a second for Watford in the 34th minute when Matej Vydra returned the favour from the earlier goal to allow his strike partner to convert from close range.
Forest should have reduced the deficit before the break but Dexter Blackstock failed to hit the target after latching onto a loose ball inside the box.
Cristian Battocchio was inches away from extending his team's lead in fortunate fashion after the break, striking the crossbar with a miscued cross from the right side of midfield.
Vydra combined with Deeney to almost create a third Watford goal but the latter scooped his shot over the bar with Darlow looking helpless following the counter-attack.
The result was put beyond doubt with less than 20 minutes remaining as Vydra netted his second of the match with a smart finish over the head of Darlow.
Forest pushed for a consolation goal in the final stages but Manuel Almunia reacted impressively to keep out Billy Sharp's low strike as Watford secured the thee points.