 | Woody Harrelson als Arthur Poppington / Defendor |
 | Kat Dennings als Katrina Debrofkowitz |
 | Elias Koteas als Chuck Dooney |
 | Sandra Oh als Dr. Park |
 | Clark Johnson als Roger Fairbanks |
 | Michael Kelly als Paul Carter |
 | Kristin Booth als Wendy Carter |
 | Lisa Ray als Dominique Ball |
 | A.C. Peterson als Radovan Kristic |
 | Tony Nappo als Biker Cliff |
 | David Gardner als Grandpa Henry |
 | Bryan Renfro als Mr. Debrofkowitz |
 | Charlotte Sullivan als Poppington |
 | Tatiana Maslany als Olga |
 | Ron White als Judge Wilson |
| Graham Abbey als Constable Mike |
| Max Dreesen als Young Arthur |
 | Matt Gordon als Jerry |
 | James Preston Rogers als Biker Bob |
 | Michael Cram als Blake |
 | Lyriq Bent als Wayne |
 | Peter Stebbings als Doctor |
 | Dakota Goyo als Jack Carter - 9 |
 | John Paul Ruttan als Jack Carter - 4 |
| Peter Stebbings | Director |
| Peter Stebbings | Writer |
| Sara Kay | Casting |
| Nancy Klopper | Casting |
| Geoff Ashenhurst | Editor |
| Oleg M. Savytski | Production Design |
| Anthony Ianni | Art Direction |
| Gersha Phillips | Costume Design |
| Cheryl Dorsey | Set Decoration |
| David Greene | Director of Photography |
| Jenny Lewis | Casting |
| Andy Asperin | Animation |
| Nicholas Tabarrok | Producer |
| Diana Ladyshewsky | Hairstylist |
| Patricia Joyes | Script Supervisor |
| Linda Dowds | Makeup Artist |
| John Rowley | Original Music Composer |
| John Douglas Smith | Supervising Sound Editor |
| Mauro Iacobelli | Painter |
| Geoffrey Smith | Leadman |
| Katie Halliday | Sound Effects Editor |
| Rob Valeriote | Carpenter |
| Warren Appleby | Special Effects Coordinator |
| Mike McDonald | Gaffer |
| Steve Myers | Best Boy Electric |
| Andrew Shea | First Assistant Director |
| Mark Gingras | Supervising Sound Editor |
| Ron Forward | Dolly Grip |
| Kyle O'Connor | Location Manager |
| Adam Stern | Visual Effects Producer |
| Herb Reischl Jr. | Rigging Gaffer |
| Sam Bojin | Best Boy Electric |
| Susan R. Jones | Production Coordinator |
| Nick Veziris | Armorer |
| Christian T. Cooke | Sound Re-Recording Mixer |
| Sean Gilhooly | Visual Effects Coordinator |
| Marek Krawczyk | Lighting Technician |
| Eardley Wilmot | Location Manager |
| Chris Abbas | Title Designer |
| Charlie Finlay | Music Editor |
| Sarah Dodd | Story Editor |
| Alan Letts | Construction Coordinator |
| James R. Murray | Property Master |
| Pat Cassin | Boom Operator |
| Daniel Bekerman | Production Manager |
| Tom Bjelic | Sound Designer |
| Steve Moore | Sound Re-Recording Mixer |
| Bryan Renfro | Stunt Coordinator |
| Dale Lennon | ADR & Dubbing |
| Jayson Clute | First Assistant Camera |
| Tony Guerin | Camera Operator |
| Ken Woroner | Still Photographer |
| Jonathan Billings | Key Grip |
