Joaquin Phoenix Arthur Fleck Lady Gaga Lee Quinzel Brendan Gleeson Jackie Sullivan Catherine Keener Maryanne Stewart Zazie Beetz Sophie Dumond Steve Coogan Paddy Meyers Harry Lawtey Harvey Dent Leigh Gill Gary Puddles Ken Leung Dr. Victor Liu Jacob Lofland Ricky Meline Sharon Washington Debra Kane Troy Fromin E Ward Inmate (Troy Larkins) Bill Smitrovich Judge Herman Rothwax John Lacy Arkham Guard Gattlin Griffith Masked Joker Driver Tim Dillon Arkham Guard Mike Houston Guard G.L. McQueary Head Bailiff Jimmy Smagula Guard Brian Donahue Guard Alfred Rubin Thompson Ernie Bullock Carson Higgins Junior Associate Ben van Diepen Music Class Singer Casey Burke Joker Girl Gregg Daniel Music Teacher Mac Brandt Arkham Guard George Carroll Arkham Guard Ajgie Kirkland E Ward Inmate Jimmy Walker Jr. E Ward Inmate June Carryl Dr. Louise Beatty Don McManus Paddy Myers' Producer Angela D. Watson Jury Foreman Murphy Guyer White Chapel Minister Hudson Oz Joker Doppelganger Ray Lykins Victim's Dad Will Ropp Joker Fan #1 Ashton Moio Joker Fan #2 Frances Conroy Penny Fleck (archive footage)