Two Watford signings grabbed their first goals for the club as the Hornets ran out 3-1 winners at non-league Wealdstone.
Former Sheffield United winger Mark Yeates put his side in front at Grosvenor Vale and Chris Iwelumo doubled the visitors' lead just before the break.
Richard Jolly pulled one back for Wealdstone in the second half but another strike from substitute Marvin Sordell made sure of the win.
As Sean Dyche had confirmed earlier in the day, Prince Buaben was not involved but three of the other four new signings started for Watford.
Former Dundee midfielder Craig Forsyth started on the left and ex-Sheffield United winger Yeates was on the other flank, with Iwelumo starting up top less than 12 hours after his move from Burnley was confirmed.
Watford's first chance came in just the second minute as the ball came to Troy Deeney eight yards out but his effort was saved by former Hornets goalkeeper Jonathan North – although the offside flag was raised.
The visitors started with purpose and kept the ball well early on. Ross Jenkins was next to try his luck as his shot from distance was deflected comfortably into the arms of North.
Iwelumo started to make his prescence felt a little more as the half wore on and moments after the striker almost got in front of his marker from a Forsyth cross, he beat North to another delivery from the left, only for the ref to blow his whistle.
There were some neat little spells from the Hornets at different times during the first half and they should have tested North again in the 20th minute when a slick move released Deeney inside the box. But he opted to cross, unsuccessfully, instead of shooting.
Watford then had another two efforts in the following 30 seconds with Jenkins' blocked shot and Deeney forcing North into a decent stop at his near post.
Wealdstone's forays into the Hornets' third were few and far between early on but they had two efforts in quick succession, as Richard Jolly lofted a shot over and Tashan Jordan's strike was deflected over.
Iwelumo's hold-up play was good and he almost grabbed his first goal for the club when he headed wide from an angled cross by Jenkins.
North was by far the busier keeper and it took Wealdstone until almost the half hour mark to force Scott Loach into his first stop when the former England Under-21 keeper comfortably held David Hick's low strike from 20 yards.
The Hornets finished the half strongly though and two new boys scored for the Hornets before the half came to a close.
Not long after Forsyth had a shot trickle wide, Eustace intercepted a pass to release Yeates and the former Sheffield United man dribbled into the box and curled his right-footed shot into the far post to break the deadlock.
Yeates then almost set up Deeney, whose neat flick was deflected just wide, and from the resulting corner, Forsyth had a powerful shot blocked.
Iwelumo was causing real problems and he forced North into the stop of the half with a thunderous shot from 18 yards.
The new arrival from Burnley got his goal though as good wide play from Lee Hodson saw Iwelumo direct his volley into bottom corner expertly, despite Hodson's cross being deflected.
The visitors made just one change at the break as Marvin Sordell came on for Lloyd Doyley, with Forsyth moving to left back and Deeney dropping to right midfield.
Watford started the second period flying as Iwelumo fired wide of the near post less than two minutes in and then North needed to make a great double save.
Yeates curled a 20 yard strike against the crossbar which Deeney reacted quickest to. North saved well to deny the former Walsall man but his second stop to deny Iwelumo was outstanding – to keep the score 2-0.
Yeates was lively and would have hoped to have done better after beating a few players on the edge of the area, only to drag his shot wide Wealdstone had been under pressure but almost equalised in a matter of minutes.
Alex Dyer showed good trickery to release Jolly inside Adrian Mariappa and the striker's early shot beat Loach at his near post.
And the home side almost levelled when Mariappa's header did not clear the area and Nikki Ahamed smashed a shot which Loach needed to parry away.
Watford made nine changes on 66 minutes, with Scott Loach being the only one out of the starting XI to remain on the pitch as the visitors switched to a 4-3-3 formation.
The game was a little flat for a while but Watford made it 3-1 a little out of the blue with 11 minutes remaining. Former Wealdstone loanee Gavin Massey passed to another in Sordell and his sharp turn and quickly-taken finish from just outside the area beat North.
Watford picked up the pace in the final ten minutes and Sordell was not far from grabbing a second when he fired past the far post from a tight angle.
Sordell then turned provider as he sent in a low cross which was just inches too far ahead of the diving Britt Assombalonga.
Walker fired over from distance twice in a matter of minutes, Piero Mingoia curled a free kick past the post and Chez Isaac called North into action again from distance, but the Hornets couldn't add a fourth.
Wealdstone: North; Hammond (Conti), Cronin, Locke, Chappell; Ahamed, Dyer, Hicks (Lumsden), Jordan (Wallace); Dean (Knight), Jolly (Beardsworth).
Watford: Loach; Hodson (Thompson 66), Mariappa (Mirfin 66), Taylor (Bennett 66), Doyley (Sordell 45); Yeates (Assombalonga 66), Eustace (Isaac 66), Jenkins (Walker 66), Forsyth (Oshodi 66); Iwelumo, Deeney (Mingoia 66), (Massey 66).