The story of August Pullman – a boy with facial differences – who enters fifth grade, attending a mainstream elementary school for the first time.
| Auggie | Jacob Tremblay |
| Isabel | Julia Roberts |
| Nate | Owen Wilson |
| Via | Izabela Vidovic |
| Jack Will | Noah Jupe |
| Summer | Millie Davis |
| Julian | Bryce Gheisar |
| Mr. Tushman | Mandy Patinkin |
| Miranda | Danielle Rose Russell |
| Mr. Browne | Daveed Diggs |
| Teenage Doctor | Mark Dozlaw |
| Nurse | Rukiya Bernard |
| Neonatologist | Jennifer March |
| Charlotte | Elle McKinnon |
| Amos | Ty Consiglio |
| Miles | Kyle Breitkopf |
| Henry | James A Hughes |
| Darth Sidious | J. Douglas Stewart |
| Ms. Petosa | Ali Liebert |
| Dodgeball Player | Joseph Gordon |
| Cute Guy | Cameron Roberts |
| Ella | Erika McKitrick |
| Justin | Nadji Jeter |
| Mr. Davenport | Ben Immanuel |
| School Photographer | Jason McKinnon |
| Reid | Izzy Lieberman |
| Rebecca | Hannah Hoberman |
| Chewbacca | Michael Alan Healy |
| Grans | Sônia Braga |
| Jack Will's Mom | Nicole Oliver |
| Ximena Chin | Emily Delahunty |
| Savanna | Lucia Thain |
| Maya | Sasha Neuhaus |
| Miranda's Mom | Rachel Hayward |
| Guy on Bus | Callahan Brebner |
| Our Town Player | Caleb Gordon |
| Our Town Player | Grayson Maxwell Gurnsey |
| Our Town Player | Emily Giannozio |
| Our Town Player | Haley Goldin |
| Via (Age 4) | Maccie Margaret Chbosky |
| Science Fair Judge | Victoria V. Cruz |
| Julian's Mom | Yan-Kay Crystal Lowe |
| Julian's Dad | Steve Bacic |
| Camp Counsellor | Jason Tremblay |
| Eddie | William Dickinson |
| Michelle | Emma Tremblay |
| Danny | Armen Bagdasarov |
| Lina Annan | Lidya Jewett |
| Angela | Kaelyn Breitkopf |
| Classmate (uncredited) | Brayden Snow |
| School Kid (uncredited) | Andre Robinson |
| School Kid (uncredited) | Alyssa Andronyk |
| Simon Stimson (uncredited) | Wilson Chieng |
| Classmate (uncredited) | Dallas Snow |
| Classmate (uncredited) | Justin Snow |
| Classmate (uncredited) | Kayzhia Snow |
| Classmate Parent (uncredited) | Amber Snow |
| Classmate (uncredited) | Elayna Sing |
| Parent (uncredited) | Ann Evans |
| Daughter at Coney Island Beach (uncredited) | Abigail Friend |
| Boy in Red (uncredited) | Razvan Orban |
| Parent (uncredited) | Kari Staten |
