Alex Lawther as Billy Bloom

Ian Nelson as Flip

AnnaSophia Robb as Blah Blah Blah

Celia Weston as Florence

Abigail Breslin as Lynette

Bette Midler as Muv

Larry Pine as William

Christopher Dylan White as Bernard

Willa Fitzgerald as Tiffany Tarbell

Michael Park as Principal Onnigan

John McEnroe as Coach Carter

Mickey Sumner as Dr. Veronica Vickers

Wally Dunn as Mr. Reamer

Marceline Hugot as Mrs. Monusky

Charlotte Ubben as Sesame

Olli Haaskivi as Tour Guide

Laverne Cox as Felicia Watts

Anatasiya Garvey as Katya

Eddie Schweighardt as Young Billy

Daniel Bellomy as Bo-Bo