Despite being Ole Gunnar Solskjaer's first game as United's permanent manager, it was far from plain-sailing for the hosts who were made to work hard by the visitors.
United took the lead through Marcus Rashford on 28 minutes, the forward calming finishing in a one-on-one with Watford's Ben Foster.
Anthony Martial made sure of the win in the second half, hitting home with 18 minutes left on the clock, before Abdoulaye Doucoure pulled one back in the dying minutes of the match.
So how did the two teams fare? See the gallery below for our player ratings.
Player ratings: Manchester United vs Watford
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