The Hornets, who have now lost four of their last six and drawn the other two, failed to find a way through against their equally out-of-sorts opponents.
Boro have at least picked up a solitary win in their last seven league outings, but scoring goals continues to be a problem for the Smoggies as they were again made to pay.
It could have been a different game entirely had Etienne Capoue made the most of his chance inside the opening 10 minutes, only for the midfielder to see Victor Valdes quickly pounce in front of goal.
Christian Stuani prodded the ball home for the visitors soon after but saw the attempt ruled out for offside, while up the other end Boro reacted quickest once Valdes spilled Abdoulaye Doucoure's strike.
Both teams were targeting the three points in London, and Boro so nearly took a giant step towards taking them when Stuani lofted the ball over the head of Heurelho Gomes and onto the roof of the net.
Christian Kabasele and Stefano Okaka also had openings of their own, with the latter at least testing Valdes with his header, and Capoue also curled narrowly wide as the hosts pushed for a breakthrough.
There was to be a big talking point 13 minutes from time when Okaka went down inside the box, but he was booked for simulation and that almost acted as a turning point as Watford debutant Tom Cleverley struck the foot of the post moments later.
The final chances of the game fell the way of Troy Deeney and Kabasele, yet neither could capitalise and in the end the spoils were shared at Vicarage Road. body check tags ::