Margot Robbie (Dr. Harleen Quinzel / Harley Quinn), Mary Elizabeth Winstead (Helena Bertinelli / La Chasseuse), Jurnee Smollett-Bell (Dinah Lance / Black Canary), Rosie Perez (Renee Montoya), Ewan McGregor (Roman Sionis / Black Mask), Derek Wilson (Tim Evans), Chris Messina (Victor Zsasz), Charlene Amoia (Maria Bertinelli), Bojana Novakovic (Erika), Ali Wong (Ellen Yee), Dana Lee (Doc), Steven Williams (Patrick Erickson), Robert Catrini (Stefano Galante), Matthew Willig (Happy), Daniel Bernhardt (Sionis' Chauffeur), François Chau (Mr. Keo), Anthony Molinari (Mafiosi), Joe Bucaro III (Carlos Rossi), Sam Hargrave (Söldner), Dennis Keiffer (Söldner), Anna Mikami (Miss Keo), Nico Greetham (junger Goon), Gerald Downey (Richter), Bruno Oliver (Sal), Michael Masini (Officer Dargo), Eddie Alfano (Helenas Leibwächter), Simon Rhee (Zellenwächter)