Vakoun Bayo is Watford's leading scorer with nine goals so far this season
Vakoun Bayo's double lifted Watford above West Brom in the Championship play-off race as they inflicted the Baggies' first defeat in 13 games.
Bayo headed in Rocco Vata's cross to give the Hornets a first-half advantage and the same pair combined again to make it 2-0 soon after the break.
Midfielder Jayson Molumby pulled one back from close range to revive Albion's hopes but, despite forcing a wave of corners during the closing stages, they could not manufacture an equaliser.
Watford held on to clinch their eighth win in 10 home games and move up to seventh, level on points with sixth-placed Middlesbrough.
The home side made changes to their forward line, with teenager Vata one of four fresh starters after scoring their equaliser in the midweek 1-1 draw at Hull, while the Baggies reverted to a three-man defence as skipper Kyle Bartley returned from injury.
It was Vata who went closest to breaking the deadlock after a tentative start, controlling the ball when Jeremy Ngakia's cross was half-cleared and lashing a right-foot volley against the crossbar.
West Brom began to build good spells of possession without genuinely troubling Daniel Bachmann, with Darnell Furlong and Uros Racic both having attempts off target.
The Hornets edged in front when the wily Giorgi Chakvetadze opened up Albion's backline and released Vata, who supplied the cross for Bayo to head down and beyond Alex Palmer.
The visitors finished the first half strongly as Bachmann clawed away Karlan Grant's angled drive but another opening for the same player, created by Callum Styles and Josh Maja, stuck under his feet as he looked to unleash a shot.
However, the momentum swung decisively back in Watford's favour after the restart as Vata skipped down the left flank once again and his cross was chested down by Bayo, who swivelled to volley into the bottom corner.
Watford pushed for a third as Chakvetadze's piercing run and shot deflected tamely into Bachmann's gloves and Kwadwo Baah was denied by Torbjorn Heggem's block.
West Brom halved the deficit as Mikey Johnston's drive rebounded for Molumby to slot home, with Bachmann flinging out a hand too late to prevent the ball crossing the line – and the home side suddenly found themselves under pressure.
Another Johnston run set up John Swift, who tested Bachmann with a drive from distance, and Darnell Furlong's injury-time header from a corner flew straight at the keeper as Tom Cleverley's side saw out the game safely.
Post-match reaction
Watford head coach Tom Cleverley told BBC Three Counties Radio:
"We knew the test we were facing and we've really risen to the challenge. It's two teams with the same objectives and, with everyone around us winning yesterday, the pressure was compounded.
"We really wanted to take the game to them and had so many good pieces of play that led to dangerous moments around the box. On paper the team was very attacking and very young today and we asked a couple of players to do really big shifts.
"I thought (Kwadwo) Baah and (Rocco) Vata were excellent out of possession, we know what they bring to the team but doing the responsible job they did today meant we could go to a back four and the team performance was excellent.
"I'm really happy for (Vakoun) Bayo, he's a player who sacrifices himself for the team but let's not discount that he's got nine in the league – he's having a really productive season in front of goal."
West Brom head coach Carlos Corberan told BBC WM 95.6:
"I think we did enough in the first half to score a goal. In the counter-attacks a team like Watford who have speed are very difficult to stop.
"They started the second half better than us, it's true that they scored one goal where I saw a foul – the referee didn't think the same. At that moment it was more difficult to achieve the result we wanted to achieve.
"In the last 10 minutes, for me, we found a way to create more volume, more corners, but we should have created more in the game.
"I think in some situations we are suffering a bit in the way we defend the box. I like to see my team managing every type of game situation better and when you concede two goals, there are situations you need to fix."
