Joaquin Phoenix Arthur Fleck / Joker Robert De Niro Murray Franklin Zazie Beetz Sophie Dumond Frances Conroy Penny Fleck Brett Cullen Thomas Wayne Shea Whigham Detective Burke Bill Camp Detective Garrity Glenn Fleshler Randall Leigh Gill Gary Josh Pais Hoyt Vaughn Marc Maron Gene Ufland Sondra James Dr. Sally Murphy Guyer Barry O'Donnell Douglas Hodge Alfred Pennyworth Dante Pereira-Olson Bruce Wayne Carrie Louise Putrello Martha Wayne Sharon Washington Social Worker Hannah Gross Young Penny Frank Wood Dr. Stoner Brian Tyree Henry Carl (Arkham Clerk) April Grace Arkham Psychiatrist Mick Szal Woman on Subway Carl Lundstedt Wall Street Three