"Stay tuned," Davis tweeted Monday of the news.
Davis will develop the film through JuVee Productions, the company she co-founded with her husband, Julius Tennon, to create more opportunities for black actors.
The film will be based on Kate Clifford Larson's 2004 book, Bound for the Promised Land: Harriet Tubman: Portrait of an American Hero.
Bound for the Promised Land details Tubman's life as a African-American woman who escaped slavery and became a so-called "conductor" on the Underground Railroad, a chain of safe houses used to guide slaves to freedom.
Tubman went on to become a Union spy during the Civil War.
Davis currently stars in ABC's How to Get Away With Murder, which garnered her a SAG Award in January.