Jacob Tremblay
as Auggie

Julia Roberts
as Isabel

Owen Wilson
as Nate

Izabela Vidovic
as Via

Noah Jupe
as Jack Will

Millie Davis
as Summer

Bryce Gheisar
as Julian

Mandy Patinkin
as Mr. Tushman

Danielle Rose Russell
as Miranda

Daveed Diggs
as Mr. Browne

Mark Dozlaw
as Teenage Doctor

Rukiya Bernard
as Nurse

Jennifer March
as Neonatologist

Elle McKinnon
as Charlotte

Ty Consiglio
as Amos

Kyle Breitkopf
as Miles

James A Hughes
as Henry

J. Douglas Stewart
as Darth Sidious

Ali Liebert
as Ms. Petosa

Joseph Gordon
as Dodgeball Player

Cameron Roberts
as Cute Guy

Erika McKitrick
as Ella

Nadji Jeter
as Justin

Ben Immanuel
as Mr. Davenport

Jason McKinnon
as School Photographer

Izzy Lieberman
as Reid

Hannah Hoberman
as Rebecca

Michael Alan Healy
as Chewbacca

Sônia Braga
as Grans

Nicole Oliver
as Jack Will's Mom

Emily Delahunty
as Ximena Chin

Lucia Thain
as Savanna

Sasha Neuhaus
as Maya

Rachel Hayward
as Miranda's Mom

Callahan Brebner
as Guy on Bus

Caleb Gordon
as Our Town Player

Grayson Maxwell Gurnsey
as Our Town Player

Emily Giannozio
as Our Town Player

Haley Goldin
as Our Town Player

Maccie Margaret Chbosky
as Via (Age 4)

Victoria V. Cruz
as Science Fair Judge

Yan-Kay Crystal Lowe
as Julian's Mom

Steve Bacic
as Julian's Dad

Jason Tremblay
as Camp Counsellor

William Dickinson
as Eddie

Emma Tremblay
as Michelle

Armen Bagdasarov
as Danny

Lidya Jewett
as Lina Annan

Kaelyn Breitkopf
as Angela

Gidget
as Daisy

Brayden Snow
as Classmate (uncredited)

Andre Robinson
as School Kid (uncredited)

Alyssa Andronyk
as School Kid (uncredited)

Wilson Chieng
as Simon Stimson (uncredited)

Dallas Snow
as Classmate (uncredited)

Justin Snow
as Classmate (uncredited)

Kayzhia Snow
as Classmate (uncredited)

Amber Snow
as Classmate Parent (uncredited)

Elayna Sing
as Classmate (uncredited)

Ann Evans
as Parent (uncredited)

Abigail Friend
as Daughter at Coney Island Beach (uncredited)

Razvan Orban
as Boy in Red (uncredited)

Kari Staten
as Parent (uncredited)