Magee was nominated for a 2004 Academy Award and a Golden Globe for Finding Neverland. Along with Simon Beaufoy, he wrote the screenplay for Miss Pettigrew Lives for a Day starring Frances McDormand and Amy Adams, which was released in 2008.
His screen adaptation of the novel Life of Pi by Yann Martel was directed by Ang Lee, released in 2012, and earned him a Satellite Award for Best Adapted Screenplay and a nomination for the Academy Award for Best Adapted Screenplay.
He wrote the screenplay for the Disney musical Mary Poppins Returns, directed by Rob Marshall, with music by Marc Shaiman and lyrics by Marc Shaiman and Scott Wittman. The film stars Emily Blunt and Lin-Manuel Miranda, and was released on December 19, 2018.
Also in December of that year, two months after the announcement that Netflix was producing a new series of adaptations based on the Narnia books, Magee confirmed via Twitter that he was not involved with the new adaptations.