The science fiction comedy centres on four men from the suburbs who unite to form a neighbourhood watch group. When the quartet discover that the town is overrun by aliens, they take action to save the planet from extermination.
Ben Stiller, Vince Vaughn, Richard Ayoade and Jonah Hill star in the film, which is directed by Hot Rod and Lonely Island helmer Akiva Schaffer.
Doug Jones, Billy Crudup and Saturday Night Live's Will Forte are among the supporting cast.
The Watch opens in US cinemas on July 27 and August 29 in the UK. The film will hold a 'People's Premiere' at London's Somerset House as part of the Film4 Summer Screen series on August 19.