The first trailer for "Avengers: Doomsday" racked up 503 million views in its first 24 hours, making it the second-biggest movie trailer launch ever and Disney's most-watched trailer of all time. It sits behind only Sony's "Spider-Man: Brand New Day", which drew 719 million views, and comfortably outpaces Disney's previous best, the "Deadpool & Wolverine" Super Bowl teaser, which reached 365 million including its broadcast audience. The scale of the response underlines the huge anticipation surrounding the film, which brings together the Avengers and X-Men on screen for the first time.

The trailer launched on 20 July, ahead of Marvel's Comic-Con presentation, and followed four teaser trailers released last December. It gave fans their first extended look at the showdown between the combined superhero teams and Doctor Doom, played by Robert Downey Jr., with a cast including Chris Evans, Chris Hemsworth, Paul Rudd, Patrick Stewart, Letitia Wright and Channing Tatum. Disney also opened advance ticket sales tied to the release, taking $16.5 million on the first day, roughly double the equivalent early figures for "Deadpool & Wolverine", with premium screenings for its 18 December opening weekend already largely sold out.