Williamson started as the understudy to Kerry Washington in the 2010 Broadway play Race before succeeding Washington in the role of Susan. Later she has made her television debut appearing in an episode of The Good Wife. Williamson later guest starred on Law & Order: Special Victims Unit, Blue Bloods, and Elementary. She had a recurring roles on CBS dramaA Gifted Man from 2011 to 2012 as Autumn, and the first season of the television series Nashville as Makena. From 2014 to 2015, she had series regular role in the Cinemax network original series Banshee. In film, she has made her debut playing supporting role opposite Adepero Oduye in the 2011 drama Pariah directed by Dee Rees.
In 2016, Williamson was cast in a leading role on the VH1 drama series The Breaks. She starred as Officer Wiggins in the 2016 HBO miniseries The Night Of. In 2018, Williamson was cast in the ABC drama series The Rookie opposite Nathan Fillion.
