They're part of a new batch of SAG Awards presenters announced Friday, along with Roman Griffin Davis, Jason Bateman, Lili Reinhart and Kaitlyn Dever.
They'll join previously announced presenters including Lupita Nyong'o and Phoebe Waller-Bridge, as well as Leonardo DiCaprio, who will present the SAG Life Achievement Award to Robert De Niro.
Most of the presenters are also nominees. Johansson is nominated for best actress in a film for "Marriage Story," best supporting actress in a film for "Jojo Rabbit" and best cast in a film along with her "Jojo Rabbit" co-stars Waititi and Davis.
Brown, a four-time SAG Award winner, is nominated for best actor in a television drama for "This Is Us."
The 26th annual Screen Actors Guild Awards will be held Sunday at 8 p.m. EST at the Shrine Auditorium in Los Angeles.