The double took his tally for the season to 10, with the goals coming either side of Daniel Ayala being sent off for the visitors before the break.
Forest had an early chance to take the lead when Andy Reid swung in a dangerous free-kick but Danny Collins glanced his header just wide.
Watford threatened soon after and Elliott Ward had to be alert to block Almen Abdi's goalbound effort after the Swiss midfielder burst through the middle.
Billy Sharp spurned a glorious opportunity to hand Forest the advantage with 15 minutes gone. Chris Cohen found Simon Cox in space down the right and his low cross was turned wide by Sharp at the back post.
And they were made to pay when Guy Moussi conceded possession in the middle of the pitch. Abdi pounced to play in Vydra and the Czech made no mistake from inside the box.
Daniel Pudil's 20-yard drive once more highlighted the hosts' threat, with Lee Camp diving to his left to tip it past the post.
Forest's task was made even harder when Ayala, who was booked earlier, picked up his second yellow in the 38th minute.
Having already got away with a blatant foul on Vydra moments earlier, the defender on loan from Norwich brought down Troy Deeney on the edge of the box and was given his marching orders.
The Hornets exploited their numerical advantage to great effect just before the break, with Abdi again laying on the assist for Vydra to finish from 12 yards.
Facing an uphill battle, Forest manager Sean O'Driscoll made two changes at the interval, bringing on Adlene Guedioura and Greg Halford for Dan Harding and Reid.
Those changes failed to stem the tide of Watford attacks and it should have been 3-0 after an hour when the ball fell kindly for Pudil on the edge of the box but he snatched at the shot and cleared the bar.
Forest, to their credit, showed some resistance after that, Guedioura firing into the side-netting and Sharp dragging a shot wide from a promising position.
But Watford were worthy of their lead and remained resolute in the closing stages, sealing a fifth win in eight league games to climb into sixth place.