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:
. WATFORD, ENGLAND - SEPTEMBER 11: Marcus Tavernier of Middlesbrough battles for possession with Nathaniel Chalobah of Watford during the Sky Bet Championship match between Watford and Middlesbrough at Vicarage Road on September 11, 2020 in Watford, England. (Photo by Richard Heathcote/Getty Images)
Marcus Tavernier. Photo: Richard Heathcote
. Marcus Bettinelli - 6
Very vocal on his Boro debut and could be heard barking out instructions throughout. A few routine saves. 6 Photo: George Wood
. Djed Spence - 6
Grew into the match and caused problems on the right in the second half. Wasn’t able to pick out a team-mate with a cross though. 6 Photo: Alex Livesey
. Anfernee Dijksteel - 7
Another fine display on the right of a back three. Made some probing forward passes and linked up well with Djed Spence in the second half. 7 Photo: Clive Brunskill
. Grant Hall - 6
Lost Cathcart for the opening goal but won some important headers and interceptions after that. 6 Photo: MFC
1. Marcus Bettinelli - 6
Very vocal on his Boro debut and could be heard barking out instructions throughout. A few routine saves. 6 Photo: George Wood
2. Djed Spence - 6
Grew into the match and caused problems on the right in the second half. Wasn’t able to pick out a team-mate with a cross though. 6 Photo: Alex Livesey
3. Anfernee Dijksteel - 7
Another fine display on the right of a back three. Made some probing forward passes and linked up well with Djed Spence in the second half. 7 Photo: Clive Brunskill
4. Grant Hall - 6
Lost Cathcart for the opening goal but won some important headers and interceptions after that. 6 Photo: MFC