In 2013, Sinclair starred in the two episodes of HBO's documentary series Masterclass.
In 2014, Sinclair played the role of Kim Carson in the one episode of NBC's Revolution. She also played the role of Tasha Williams in the three episodes of TNT's Rizzoli & Isles.
In 2015, Sinclair played Angela in the Jake Schreier-directed comedy-drama film Paper Towns, along with Nat Wolff and Cara Delevingne. The film is an adaptation of the novel of same name by John Green, and was released by 20th Century Fox on July 24, 2015.
In 2016, Sinclair starred as Anna, a surrogate mother, in the thriller film When the Bough Breaks, directed by Jon Cassar. The film was released on September 9, 2016 by Screen Gems.
On February 5, 2018, Sinclair was cast as Rosalind Walker in the upcoming Netflix series based on Chilling Adventures of Sabrina.