Yoram Honig of the Jerusalem Film Fund and a publicist for the film said Wednesday that Portman wrote the screenplay and will also star in the movie as Oz's troubled mother.
They say Portman is to arrive in October in Israel to cast local actors. The movie will be filmed in Jerusalem in early 2014.
It's not decided if the film will be shot in Hebrew or English. Honig's fund is providing $400,000.
The movie is based on Oz's 2002 autobiography, "A Tale of Love and Darkness," about his youth during Israel's founding years.
The publicist spoke on condition of anonymity to discuss the project.