For Watford, who moved up to 10th, it was their fourth successive home win and Javier Gracia’s second victory from his four games since returning as manager last month.
He will be hugely satisfied with the result as the Hornets also registered their first clean sheet at the 13th attempt.
Watford goalkeeper Egil Selvik denied Hayden Hackney to set the theme for the day before Kwadwo Baah crossed for Louza to fire home the opener after 15 minutes with his fifth goal in seven games.
Selvik was in no mood to be beaten and the Norwegian saved a free-kick from Matt Targett before he kept out a right-footed volley from Hackney.
The Hornets made it 2-0 on 32 minutes when Jeremy Ngakia crossed for Kjerrumgaard to steer the ball home.
Mamadou Doumbia thought he had registered his first of the season on 49 minutes with a 20-yard effort, but Kjerrumgaard got the final touch for his second of the afternoon.
Still Middlesbrough kept coming forward, and Watford defender Mattie Pollock did well to halt Tommy Conway before Hackney fired wide again.
Edwards and Middlesbrough knew it was not their day when Morgan Whittaker missed a tap-in at the back post.
