Arsenal boss Arsene Wenger was delighted by his side's first half display at Vicarage Road, which saw them lead 3-0 at the break thanks to goals from Mesut Ozil, Alexis Sanchez and Santi Cazorla.
Germany international Mesut Ozil returned to the first-team, which clearly gave a boost to his teammates as Arsenal dominated the early exchanges against Watford.
Cazorla scored the opener from the penalty spot after eight minutes, while Chilean forward Alexis Sanchez doubled the lead after good work from Theo Walcott on the right.
Ozil tripled the Gunners' lead on the stroke of half-time with a thumping header from close range after Alexis Sanchez whipped in a fine cross.
The result marks Arsenal's first win of the season after they fell to an opening day defeat at home to Liverpool, before entertaining Leicester in a goalless draw last weekend.
Arsène Wenger has now won 650 games as Arsenal manager. #afc pic.twitter.com/MI0Zy0nbOK
Speaking at his post-match press conference, Wenger said: "I believe we shot ourselves in the foot in the first game and were under huge pressure,
"We had two difficult away games but today I believe we had a good solid performance.
"We had a good cushion at half time. At the moment we are not completely there physically and could see that in the second half."
The Frenchman,who won his 650th game for Arsenal on Saturday, also confirmed that longstanding targetsShkodran Mustafi andLucas Perez have completed their moves to North London.
We have bought two players, Mustafi and Perez, now we can integrate them into the squad.� he added.
They've both had medicals but we need to complete the paperwork�