Boro moved up to third in the Championship after turning in a season-best performance at the Riverside.
Michael Carrick's men were in irrestible form against promotion chasing Watford, and goals from Chuba Akpom and Marcus Forss secured a deserved victory.
Boro controlled the game from the off, playing some fantastic football, and the final scoreline flattered a visiting team who found the Teessiders too hot to handle for long periods.
The win saw Boro leapfrog Watford in the table to move within 12 points of second-paced Sheffield United.
Possession
43%Shots
11Shots On Target
4Corners
5Fouls
191
0
Cards
2
0
There was a full debut for January signing Cameron Archer and a recall for Paddy McNair, who replaced the suspended Dael Fry.
Boro started brightly and Akpom had an effort deflected wide after some good early play.
Watford goalkeeper Daniel Bachmann was called upon early doors to make a save from an advancing Marcus Forss.
Boro were looking very lively up front, and Archer was denied a first goal for the club when Hamza Choudhury blocked his shot on the line.
It was an entertaining opening and Zack Steffen did well to stand tall when faced with Matheus Martins in a one-on-one.
Watford goalkeeper Bachmann kept it goalless shortly after the half-hour when Archer worked himself an opening before being denied. And Choudry was again in right place at the right time to clear the rebound when under pressure from Akpom.
There was no denying Akpon once again, though, after more great work from Archer. The loan man raced clear to test Bachmann again, and Akpom followed-up well to convert with his head.
It was almost 2-0 moments later when Watford lost possession deep in their own half and it took a desperate lunge to prevent Akpom from doubling the advantage.
Akpom was right in the thick of it and he was thwarted by Bachmann after a little collision between the two.
The second goal that Boro richly deserved came on the stroke of half-time. Hayden Hackney and Jonny Howson linked up well and Forss applied an impressive finishing touch.
Bachmann was tested early doors in the second half by Archer, and Boro continued to play some great football.
It was a little more end to end, but Archer was unlucky to send the ball over the top after good work by Tommy Smith and Riley McGree.
Hackney forced a save from Bachmann and there were shouts of handball when Choudhury cleared the rebound.
McNair was next to go close as Boro continued to dominate and he volleyed over the top after arriving at the far post to meet a Ryan Giles cross.
When Watford sub Tobi Adeyemo had sight of goal, Steffen proved equal to the angled shot.
Giles and McGree combined well again when the Australian international lifted a shot over the top.
With seven minutes left on the clock, Archer was given a standing ovation by the Riverside after turning in a terrific performance on his first start.
Middlesbrough: Steffen, Giles, Smith, McNair, Lenihan, McGree (Dijksteel 94'), Hackney, Howson, Akpom (Mowatt 93'), Forss (Watmore 72'), Archer (Crooks 84')
Subs: Crooks, Jones, Mowatt, Watmore, Roberts, Bola, Dijksteel
Watford: Bachmann, Sierralta (Bacuna 45'), Cathcart, Choudhury, Kamara, Koné (Henrique Araújo 45'), Mario Gaspar, João Ferreira (Asprilla 64'), Sarr, Davis (Adeyemo 45'), Matheus Martins (Pollock 71')
Subs: Henrique Araújo, Adeyemo, Okoye, Asprilla, Morris, Pollock, Bacuna