Variety magazine said Ms Dean, who most recently starred in this year’s Palme d’Or winning film Triangle of Sadness, died on Monday in New York from an “unexpected illness”.
Ms Dean also appeared in the DC Comics’ TV series Black Lightning.
Scott Feinberg, executive editor of The Hollywood Reporter, said her death was “a tragedy”, adding that Triangle of Sadness was “going to make her a star”.
Dean co-stars in the movie, a satirical dark comedy, opposite Harris Dickinson. After favourable pre-release reviews, it is due to be officially released in October.
She made her acting debut in 2010 in the South African film Spud and returned in the 2013 sequel “Spud 2: The Madness Continues.”
In addition to acting, Ms Dean began modelling at the age of six and signed with a professional agency at 12, appearing on magazine covers and in TV adverts and catalogues.