In 2014, Foy appeared in Erica Dunton's movie Black Eyed Dog. In February 2012, she joined the cast of James Wan's horror film The Conjuring. Shooting started on February 21 in North Carolina, and the film was released in July 2013. In February, she was also in the last episode of the second season of the horror TV series R. L. Stine's The Haunting Hour, in which she played Natalie, a girl who goes to live with her grandfather, finding out that one of the dolls is alive and has bad intentions. On October 10, 2012, Foy joined Wish You Well, the film adaptation of David Baldacci's book, where she plays the lead. On 17 November 2012 Foy was in another episode of R. L. Stine's The Haunting Hour, playing Georgia Lomin.
Foy co-starred in Christopher Nolan's Interstellar, which is about a team of explorers who travel through a wormhole in an attempt to ensure humanity's survival. She provided the voice of Violet in The Boxcar Children (2014), and also provided the voice of The Little Girl in The Little Prince (2015). On May 2015, it is confirmed that Mackenzie will be in Zhang Yimou's mystery/thriller film The Great Wall, set for release in November 2016.