According to Deadline, Harris joins previously announced cast members Cate Blanchett, Michael Fassbender, Rege-Jean Page and Marisa Abela.
Soderbergh will direct "Black Bag" from a script by David Koepp. Casey Silver and Greg Jacobs are producing the film. Focus Features acquired the project last month.
Harris, also known for playing Eve Moneypenny in James Bond films "Skyfall", "Spectre", and "No Time to Die", was most recently seen in the Showtime series "The Man That Fell To Earth".
