Samuel Barnett voiced Hans Tod in the Big Finish Doctor Who audio story The Beast of Orlok, Robin Yeadon in Nightshade, and Norton Folgate in Ghost Mission, The Torchwood Archive, Outbreak and Goodbye Piccadilly.

Barnett was part of the original Royal National Theatre cast of the play The History Boys, which also featured Sacha Dhawan, James Corden, Russell Tovey, and Samuel Anderson in main roles. Barnett also portrayed the character Dirk Gently in the BBC America/Netflix series Dirk Gently's Holistic Detective Agency, based on former Doctor Who writer Douglas Adams's novel series.