 | Joaquin Phoenix als Arthur Fleck / Joker |
 | Lady Gaga als Harleen Quinzel / Harley Quinn |
 | Brendan Gleeson |
 | Catherine Keener |
 | Zazie Beetz als Sophie Dumond |
 | Steve Coogan |
 | Harry Lawtey |
 | Leigh Gill als Gary |
 | Ken Leung |
 | Jacob Lofland |
 | Sharon Washington als Social Worker |
 | Troy Fromin als E Ward Inmate (Troy Larkins) |
 | Bill Smitrovich als Judge Herman Rothwax |
| Todd Phillips | Director |
| Todd Phillips | Writer |
| Scott Silver | Writer |
| Bill Finger | Characters |
| Bob Kane | Characters |
| Jerry Robinson | Characters |
| Emma Tillinger Koskoff | Producer |
| Joseph Garner | Producer |
| Todd Phillips | Producer |
| Francine Maisler | Casting |
| Arianne Phillips | Costume Design |
| Bryan Mendoza | Utility Sound |
| Steven Morrow | Sound Mixer |
| Michael Kaleta | Boom Operator |
| Lori DeLapp | Costume Supervisor |
| Jason Ruder | Executive Music Producer |
| Ken Haber | Location Scout |
| Aaron Hurvitz | Location Scout |
| Gregory Irwin | First Assistant "A" Camera |
| John Reynolds | Best Boy Grip |
| Rick Chavez | Assistant Property Master |
| Lawrence Sher | Director of Photography |
| Hildur Guðnadóttir | Original Music Composer |
| Mark Friedberg | Production Design |
| Sydnie Ponic | Art Direction |
| Sarah Contant | Set Designer |
| Noelle King | Set Designer |
| Hogan Lee | Set Designer |
| Michael Thurman | Set Dresser |
| Shauna Duggins | Stunts |
| Mallory Thompson | Stunts |
| Georgia Kacandes | Executive Producer |
| Jeff Groth | Editor |
| Mia Bauman | Makeup Artist |
| Mitchell Beck | Key Hair Stylist |
| Jessie Bishop | Makeup Artist |
| John Damiani | Key Makeup Artist |
| Jacqueline Fernandez | Makeup Artist |
| Heather Galipo | Makeup Artist |
| Kay Georgiou | Hair Designer |
| Brian Kinney | Makeup Artist |
| Nicki Ledermann | Makeup Designer |
| Alyssa Morgan | Makeup Artist |
| Martina Sykes | Makeup Artist |
| Sweet P. Vaughn | Makeup Artist |
| Georgia Kacandes | Unit Production Manager |
| Randy Manion | Unit Production Manager |
| David Webb | First Assistant Director |
| Trevor Tavares | Second Assistant Director |
| Travis Rehwaldt | First Assistant Director |
| Ryan Robert Howard | Second Assistant Director |
| Brian Machleit | Stunt Coordinator |
| Michael Uslan | Executive Producer |
| Mark Friedberg | Executive Producer |
| Bruce Timm | Characters |
| Paul Dini | Characters |
| Nitasha Bhambree | Stunts |
| Randall Poster | Music Supervisor |
| George Drakoulias | Music Supervisor |
| Scott Silver | Executive Producer |
| Jason Ruder | Executive Producer |
