Nottingham Forest found Matej Vydra too hot to handle for the second time in five weeks.
The Czech Republic international scored both of Watford’s goals in their win over Forest at Vicarage Road before Christmas.
And he bagged another brace as Gianfranco Zola’s men boosted their promotion hopes – and dented Forest’s – with a convincing win at The City Ground.
Vydra set Watford on their way with a 20th minute goal and after Troy Deeney had added a second before half-time, the 20 year old killed off Forest’s challenge 18 minutes from time.
Alex McLeish made one change to his starting line-up as he recalled Dexter Blackstock at the expense of Radi Majewski, while new signing Darius Henderson was named among the substitutes.
After a lack-lustre start to the game from both sides Watford burst into life in the 17th minute as they came close to forging the breakthrough. Deeney span away from his marker Danny Collins to get on the end of Daniel Pudil’s incisive ball forward but the striker planted his shot wide of the target.
But the visiting supporters only had to wait three more minutes to launch their celebrations. Collins’ attempted headed clearance struck one of his own players and fell kindly for Watford and when Deeney pulled the ball back from the bye-line, Vydra was on hand to sidefoot home.
Karl Darlow made a stunning save to deny Watford a second as he dived low down to his right to keep out Almen Abdi’s shot from the edge of the area after the visitors had sliced Forest open again.
And Lloyd Doyley and Joel Ekstrand had shots cleared off the line as McLeish’s men failed to deal with the resultant corner.
That was a let-off but Watford extended their lead 11 minutes before the break as Forest again failed to deal with their pace and movement.
Collins was given a glimpse of the Watford goal when Manuel Almunia spilled a Chris Cohen free-kick under pressure from Blackstock but when the visitors countered, Nathaniel Chalobah sent Vydra clear and the Czech Republic international had the presence of mind to square for Deeney to add the finishing touch.
Collins headed wide of Almunia’s target from a Cohen free-kick and Simon Cox was inches away with a shot from the edge of the area as Forest looked for a response.
But Blackstock squandered their best opportunity of the first half just moments before the break as he failed to find the target after Cohen’s cross from the left had found him unmarked in the six-yard box.
McLeish made a change at the start of the second as he replaced Gillett with Andy Reid, fit again after a two-match lay-off with a hamstring problem.
Marco Cassetti went close to gifting Forest a lifeline as his bundled a Cox cross from the right just inches wide of his own goal, while at the other end a right-wing centre from Cristian Battocchio threatened to catch out Darlow but the crossbar came to his rescue.
Vydra went close to claiming his second of the afternoon as his free-kick from 20 yards out beat Darlow but found the side-netting.
Deeney squandered a golden opportunity to strengthen Watford’s grip on the game as he fired over the bar after his strike partner Vydra had sent him clear of Forest’s back four.
McLeish made his second change of the afternoon just after the hour mark as Majewski replaced Cox and moments later Almunia made a regulation save to keep out a half-volley from Sharp that bounced wickedly up off the turf.
Vydra wrapped up Watford’s win 18 minutes from time as he bagged his second by calmly lobbing the on-rushing Darlow after Abdi’s superb through ball had left him with just the ‘keeper to beat.
Henderson joined the action for his debut 14 minutes from time and although Sharp forced Almunia to make a smart save in stoppage time, it was an afternoon to forget for all those of a Forest persuasion.
Forest: Darlow, Jara Reyes, Ward, Collins (c), Halford, Gillett (Reid 46'), Cohen, Lansbury, Cox (Majewski 61'), Blackstock (Henderson 77'), Sharp
Subs not used: Evtimov, Harding, McGugan, Greening
Bookings: Cox 51'
Watford: Almunia (c), Deeney, Doyley, Pudil, Vydra, Abdi, Cassetti (Hall 69'), Nosworthy, Battocchio (Hogg 78'), Chalobah (Yeates 86'), Ekstrand
Subs not used: Bond, Eustace, Geijo, Forestieri
Scorers: Vydra 20' 72', Deeney 34'
Bookings: Doyley 26', Chalobah 36'
Referee: Andy Haines
Attendance: 20,732 (Away: 1,754)