Margot Robbie Harleen Quinzel / Harley Quinn Idris Elba Robert DuBois / Bloodsport John Cena Christopher Smith / Peacemaker Joel Kinnaman Colonel Rick Flag Sylvester Stallone Nanaue / King Shark (voice) Viola Davis Amanda Waller David Dastmalchian Abner Krill / Polka-Dot Man Daniela Melchior Cleo Cazo / Ratcatcher 2 Michael Rooker Brian Durlin / Savant Jai Courtney George 'Digger' Harkness / Captain Boomerang Peter Capaldi Gaius Grieves / The Thinker Alice Braga Sol Soria Pete Davidson Richard Hertz / Blackguard Joaquín Cosío Mayor General Mateo Suarez Juan Diego Botto Presidente General Silvio Luna Storm Reid Tyla DuBois Nathan Fillion Cory Pitzner / T.D.K. Taika Waititi Ratcatcher Steve Agee John Economos / On-Set King Shark Sean Gunn Weasel / Calendar Man John Ostrander Doctor Fitzgibbon Flula Borg Gunter Braun / Javelin Mayling Ng Mongal Stephen Blackehart Briscoe Tinashe Kajese Flo Crawley Jennifer Holland Emilia Harcourt Fernando Martinez Sliced Dome Soldado Dee Bradley Baker Sebastian (voice) Natalia Safran Kaleidoscope Rey Hernandez Teniente Ray Benitez Coronel Jonathan Fritschi Delicious Hot Dog Guerrilla Josh Ventura Astronaut Gerardo Davila General Vera Mikaela Hoover Camila Lynne Ashe Polka-Dot Man's Mom Julio Cesar Ruiz Milton Maya Le Clark Young Cleo Andrea Andrade La Gatita Waitress Giovanni Rodriguez Texting Torturer Sergio Carlo Isabella's Second Kenneth Trujillo Bespectacled Soldado Randy Havens Star-Crossed Man Terence Rosemore Crew Chief Pom Klementieff La Gatita Amable Dancer (uncredited)