King was born in Los Angeles, California. She received a BFA in Acting from the University of California, Santa Barbara, and an MFA from Yale University's prestigious School of Drama in 2010. At Yale University, King performed in a number of productions, including A Midsummer Night's Dream, Little Shop of Horrors and Angels in America.
King appeared in several short films before landing guest roles on the CBS procedurals Blue Bloods and Person of Interest. Her big break came in 2012 when she was cast as new surgical intern Cassandra Kopelson on the CW drama Emily Owens, M.D. The series was canceled after a single season in 2013. She later starred in the Amazon Studios comedy pilot The Onion Presents: The News. King also played Wendell Pierce's daughter Abigayle in the independent film Four, released on September 13, 2013. Along with her castmates, she won a Los Angeles Film Festival Award for her role in this movie. In March 2014, King landed a regular role as Michaela in Shonda Rhimes' ABC legal drama series How to Get Away with Murder.