Jacob Tremblay
Auggie Pullman
Julia Roberts
Isabel Pullman
Owen Wilson
Nate Pullman
Izabela Vidovic
Via Pullman
Noah Jupe
Jack Will
Millie Davis
Summer Dawson
Bryce Gheisar
Julian Albans
Mandy Patinkin
Mr. Tushman
Danielle Rose Russell
Miranda Navas
Daveed Diggs
Mr. Browne
Elle McKinnon
Charlotte Cody
Ali Liebert
Ms. Petosa
Nadji Jeter
Justin Hollander
Ty Consiglio
Amos Conti
Kyle Breitkopf
Miles Noury
James A Hughes
Henry Joplin
Nicole Oliver
Mrs. Will
Rachel Hayward
Mrs. Navas
Yan-Kay Crystal Lowe
Melissa Albans
Steve Bacic
Julian Albans, Sr.
Ben Immanuel
Mr. Davenport
Sônia Braga
Grandma
Izzy Lieberman
Reid Kingsley
Hannah Hoberman
Rebecca
Erika McKitrick
Ella
Lucia Thain
Savanna Wittenberg
Emily Delahunty
Ximena Chin
Sasha Neuhaus
Maya Markowitz
William Dickinson
Eddie Johnson
Armen Bagdasarov
Danny
Emma Tremblay
Michelle
Lidya Jewett
Lina Annan
Kaelyn Breitkopf
Angela
Emily Giannozio
Rebecca Gibbs
Haley Goldin
Mrs. Gibbs
Cameron Roberts
James
Grayson Maxwell Gurnsey
Wally
Maccie Margaret Chbosky
Young Olivia
Gidget
Daisy
Victoria Cruz
Science Fair Judge
Laura Mozgovaya
Julian's sister
Darcy Rose Byrnes
Musical Theatre Student (voice)
Jason McKinnon
School Photographer
Brayden Snow
Classmate
Brooke D. Singleton
Additional Voices (voice)
Andre Robinson
School Kid
Alyssa Andronyk
School Kid
Jason Tremblay
Camp Counsellor
Wilson Chieng
Simon Stimson
Dallas Snow
Classmate
Justin Snow
Classmate
Kayzhia Snow
Classmate
Amber Snow
Classmate Parent
Elayna Sing
Classmate
Ann Evans
Parent
Mark Dozlaw
Doogie Howser (uncredited)
Abigail Friend
Daughter at Coney Island Beach (uncredited)
Razvan Orban
Boy in red (uncredited)
Kari Staten
Parent (uncredited)
Sean Ryan Fox
Additional Voice