England Under 21 striker Theo Walcott made his first start for Arsenal after his two goals against Germany this week.
Arsenal defender Toure made it 1-0 for the Gunners, 32 minutes into the match. Henry doubled the lead in the 43rd minute.
Adebayor finished the scoring and made it 3-0 to Arsenal in the 67th minute, after a great foreplay by Cesc Fabregas and Henry.
Arsenal go fourth on the Premiership table, while Watford stay second bottom.
Teams:
Arsenal:
Lehmann, Djourou, Gallas, Toure, Hoyte, Walcott, Fabregas, Silva, Rosicky, Adebayor, Henry. Subs: Almunia, Van Persie, Hleb, Song Billong, Clichy.
Watford:
Foster, Doyley, DeMerit, Shittu, Stewart, Smith, Mahon, Francis, Bouazza, King, Young. Subs: Lee, Mackay, Henderson, Powell, Spring.