Sidney began acting in 2012, appearing in the short film The Babysitters. She next appeared in Roots, and appeared in American Horror Story: Roanoke as the reenactment of Flora Harris. Sidney next appeared in Fences, the film with four 2017 Oscar nominations, including one win, directed by Denzel Washington, opposite Washington and Viola Davis, and Hidden Figures, the film which received three 2017 Oscar nominations, directed by Theodore Melfi, both of which were released in December 2016. Sidney next starred in Fast Color directed by Julia Hart, opposite Lorraine Toussaint and Gugu Mbatha-Raw, which had its world premiere at South by Southwest on March 10, 2018.