| Bill Skarsgård | Pennywise |
| Sophia Lillis | Young Beverly |
| Jessica Chastain | Beverly Marsh |
| James McAvoy | Bill Denbrough |
| Jay Ryan | Ben Hanscom |
| Bill Hader | Richie Tozier |
| Isaiah Mustafa | Mike Hamlon |
| James Ransone | Eddie Kaspbrak |
| Andy Bean | Stanley Uris |
| Jaeden Martell | Young Bill Denbrough |
| Wyatt Oleff | Young Stanley Uris |
| Jack Dylan Grazer | Young Eddie Kaspbrak |
| Finn Wolfhard | Young Richie Tozier |
| Chosen Jacobs | Young Mike Hanlon |
| Jeremy Ray Taylor | Young Ben Hanscom |
| Teach Grant | Henry Bowers |
| Nicholas Hamilton | Young Henry Bowers |
| Javier Botet | Hobo/The Witch |
| Xavier Dolan | Adrian Mellon |
| Taylor Frey | Don Hagarty |
| Molly Atkinson | Myra/Sonia Kaspbrak |
| Joan Gregson | Mrs. Kersh |
| Stephen Bogaert | Alvin Marsh |
| Luke Roessler | Dean |
| Stephen King | Shopkeeper |
| Peter Bogdanovich | Peter - Director |
| Will Beinbrink | Tom |
| Jess Weixler | Audra Phillips |
| Martha Girvin | Patty |
| Ryan Kiera Armstrong | Victoria Fuller |
| Jackson Robert Scott | Dead Georgie |
| Jake Weary | Webby |
| Katie Lunman | Chris Unwin |
| Kelly VanDerBurg | Victoria's Mom |
| Jason Fuchs | Richie's Manager |
| Joe Bostick | Mr. Keene |
| Megan Charpentier | Young Gretta |
| Juno Rinaldi | Gretta |
| Neil Crone | Chief Borton |
| Ry Prior | Connor |
| Owen Teague | Dead Hockstetter |
| Jake Sim | Belch Huggins |
| Logan Thompson | Victor Criss |
| Connor Smith | Carny |
| Amanda Zhou | Waitress |
| Rob Ramsay | Meaner Nurse |
| John Connon | John Koontz (Juniper Hill Security) |
| Doug MacLeod | Head Honcho |
| Brandon Crane | Big Guy |
| Erik Junnola | Scuzzah |
| Josh Madryga | Scuzzah |
| Peter George Commanda | Shokopiwah Shaman |
| Kiley May | Shokopiwah Women |
| Lisa Cromarty | Shokopiwah Women |
| Kevin Allan Hess | Shokopiwah Men |
| Stephen R. Hart | Shokopiwah Men |
| Rocky L. Burnham | Shokopiwah Men |
| Billy Merasty | Shokopiwah Men |
| Sladen Peltier | Shokopiwah Young Boy |
| Ari Cohen | Stanley's Dad |
| Alex Bird | Theatre P.A. |
| Brody Bover | Shouting Kid |
| Edie Inksetter | Shouting Kid's Mom |
| Martin Julien | Janitor |
| Sonia Maria Chirila | Fishtank Girl |
| Colin McLeod | Bully |
| Declan Prior | Bully |
| Marko Vujicic | Bully |
| Eric Woolfe | Nurse |
| Kate Corbett | Dean's Mom |
| Shawn Storer | Dean's Dad |
| Janet Porter | Richie's Mom |
| Scott Edgecombe | Customer |
| Anthony Ulc | The Butcher |
| J. Bogdan | Swearing Patient |
| Louise Stratten | Audra's Assistant |
| Laura Thorne | Production Assistant |
| Thomas Duhig | Assistant Director |
| Carla Guerrier | Police Officer |
| Liam MacDonald | Dean's Friend |
| Chris D'Silva | Dean's Friend |
| Torian Matthew Cox | 4-Year-Old Young Mike |
| Tristan Levi Cox | 4-Year-Old Young Mike |
| Lola DelReHudson | Betty Ripsom's Legs |
| Thiago dosSantos | Twitchy Man |
Technical Credits
| Andy Muschietti | Director |
| Sylvain Arseneault | Sound Mixer |
| Paul Denham Austerberry | Production Designer |
| Jason Ballantine | Editor |
| Robert Beal | Sound Mixer |
| Richard Brener | Executive Producer |
| Roberto Campanella | Choreography |
| Nigel Churcher | Art Director |
| Gary Dauberman | Executive Producer,Screenwriter |
| Rich Delia | Casting |
| Aaron Dinsmore | Special Effects |
| Marty P. Ewing | Executive Producer |
| Jason Fuchs | Co-producer |
| Stephanie Gorin | Casting |
| Seth Grahame-Smith | Executive Producer |
| Brian Hanish | Sound Mixer |
| Myron Hoffert | Asst. Director |
| Kristy Hollidge | Special Effects |
| David Katzenberg | Executive Producer |
| Jason Kenny | Special Effects |
| Michael Lerman | Asst. Director |
| Dan Lin | Producer |
| Drew Longland | Special Effects |
| Travis McConnell | Asst. Director |
| Mike Murawsky | Special Effects |
| Barbara Muschietti | Producer |
| Dave Neustadter | Executive Producer |
| Erick Ocampo | Sound/Sound Designer |
| Victoria Palmeri | Co-producer |
| Darryl Purdy | Sound Mixer |
| Darin Read | Associate Producer |
| Ted Ross | Special Effects |
| Oriana Rossi | Makeup |
| Roy Lee | Producer |
| Luis M. Sequeira | Costumes/Costume Designer |
| John Thompson | Sound Mixer |
| Randy Torres | Sound/Sound Designer |
| Checco Varese | Cinematographer |
| Benjamin Wallfisch | Score Composer |
