Hornets defender Craig Cathcart scored the only goal of the game when he headed home with just 11 minutes on the clock.
Our Boro writer Joe Nicholson has dished out his marks following the match – scroll down and flick through our picture gallery to see if you agree with his player ratings:
5. Paddy McNair - 6
Played on the left of a back three and thwarted a couple of attacks. 6 Photo: Alex Livesey
6. Marvin Johnson - 6
Didn’t have too many problems in the left wing-back position. Most of Boro’s attacks came down the opposite flank. 6 Photo: Alex Livesey
7. George Saville - 5
Struggled in the first half when Watford went on the attack. A few heavy touches. 5 Photo: James Chance
8. Jonny Howson - 7
Had to keep an eye on Ken Sema early on but got a grip of the match in the second half. Threw himself into challenges and played some searching forward passes. 7 Photo: Clive Brunskill