Watford took advantage of some woeful defending from Middlesbrough to secure their first league win of the season.
Bouazza played a part in Watford's opening goal
The Hornets went in front after just over five minutes when Hameur Bouazza's off-target shot was deflected into his own net by Jonathan Woodgate.
A weak header from George Boateng gifted a second to Watford, with Ashley Young firing his fourth of the season.
Middlesbrough rarely looked like scoring, while Darius Henderson was also denied by Mark Schwarzer's legs.
Watford suffered a blow when goalkeeper Ben Foster was forced out due to a knee problem, with Richard Lee stepping in for the in-form stopper.
But Boro's attacking efforts were so lacklustre that the home side could have probably played without a keeper in the first half and still managed to extend their run without conceding.
A third clean sheet on the trot means they have now gone 293 minutes without letting in a goal in the league.
Watford's forward line hardly set the place alight, but fortunately Middlesbrough's defence were there to offer them a helping hand.
In the sixth minute Woodgate failed to properly clear Gavin Mahon's throw and when the Boro defender stuck out his leg to try and block Bouazza's shot he deflected it past Schwarzer's despairing dive.
Middlesbrough had a glimpse of goal when Stewart Downing released Julio Arca but he screwed a left foot shot well over rather than square for Yakubu.
Tommy Smith, Jordan Stewart and Bouazza all had shots off target and Schwarzer bravely saved at the feet of the former as Watford looked for a second.
Jay Demerit blocked Yakubu's powerful shot as the first half came to an end.
Middlesbrough started the second half in brighter fashion with Downing finally forcing Lee into action 29 seconds after the interval.
But they had a let off when Young blazed over from point-blank range after the dangerous Bouazza had drilled a volley across the face of goal.
The second goal soon followed as Boateng attempted to plant a header back to Schwarzer, but he succeeded only in finding Young who turned and angled a shot past the Australian.
Watford nearly returned the favour when Stewart made a hash of trying to clear Yakubu's centre and he was relieved to see James Morrison make an equally bad attempt at controlling the cross.
Lee Cattermole's ugly half-volley summed up Middlesbrough's day and a Woodgate slip almost handed Watford a third, but Schwarzer came to his team-mate's rescue.
Watford boss Aidy Boothroyd:
"It was a good consistent performance and much more solid defensively.
"Overall I was pleased and thought we were very professional.
"We've had a solid start and we have now got to make sure we maintain that, keep getting the clean sheets, get the goals and climb the table.
"We were resolute and resilient and we just need to be a bit more ruthless in front of goal."
Middlesbrough manager Gareth Southgate:
"I've no complaints - Watford deserved it.
"We knew what to expect and when you concede that early it leaves you a mountain to climb. Our best period saw us concede the second goal.
"We've lost here, we've lost at Reading and Sheffield United so people will question our character and our attitude.
"What I am questioning is our quality. Their desire to put things right is there but we open ourselves up to that when we lose the matches we have."
Watford: Lee, Doyley, Shittu, DeMerit, Stewart, Smith, Francis, Mahon, Bouazza, Young, Henderson.
Subs Not Used: Chamberlain, Mackay, Powell, Priskin, Spring.
Goals: Woodgate 6 og, Young 60.
Middlesbrough: Schwarzer, Pogatetz, Woodgate, Huth, Arca (Morrison 46), Davies, Euell (Cattermole 68), Boateng, Downing, Yakubu, Maccarone (Graham 80).
Subs Not Used: Turnbull, Taylor.
Ref: D Gallagher (Oxfordshire).