Jason Segel (The Muppets) and David Krumholtz (Numb3rs) will join her, all playing themselves in Seth Rogen and Jay Baruchel's forthcoming comedy movie, according to The Hollywood Reporter.
Formerly known as The Apocalypse, Rogen and Evan Goldberg's directorial debut is based on the short Jay and Seth vs. the Apocalypse, in which the pair play themselves trapped in their apartment following the end of the world.
James Franco, Jonah Hill, Danny McBride and Craig Robinson have already been announced for cameos in the movie.
Parks and Recreation's Aziz Ansari was most recently revealed to make an appearance in the film.
Rumours that Watson's Harry Potter co-star Daniel Radcliffe would feature in the movie were debunked last year.
Watson is currently shooting Sofia Coppola's The Bling Ring in Los Angeles and will also be seen this year in The Perks of Being a Wallflower.
Segel and Krumholtz are long-term Rogen collaborators, with the former working with him on the 2001 show Undeclared and the latter appearing with him on Freaks and Geeks in 1999.