His first film role was in Lindsay Anderson's film If.... (1968). He also appeared in Anderson's O Lucky Man! (1973) and Britannia Hospital (1982). His other film credits include roles in Amadeus (1984), A Christmas Carol (1984), Gulag (1985), Heavenly Pursuits (1986), Little Dorrit (1987), The Great Escape II: The Untold Story (1988), Loch Ness (1996), The House of Mirth (2000), The Rocket Post (2004), Vanity Fair (2004) and Lassie (2005).
He appeared in Hamish Macbeth, as well as guest starring in Still Game. In 2005, he also appeared in the first episode of the BBC drama Bleak House. In 2011 and 2013, he played Father Richards in The Field of Blood. His most recent appearance was as Poupart in the BBC One series The Musketeers.
Pettifer is the younger brother of folk musician Linda Thompson. Pettifer has worked extensively in the theatre: writing, directing and acting. He has been in a production of The Fairy-Queen at Glyndebourne, which went to Paris and New York in 2010.
In 2015, Pettifer appeared in the crime comedy The Legend of Barney Thomson along with his Hamish Macbeth co-star Robert Carlyle.
In 2017, Pettifer appeared in "Crocodile", an episode of the fourth season of anthology series Black Mirror.
