Grace VanderWaal as Susan "Stargirl" Caraway

Graham Verchere as Leo Borlock

Karan Brar as Kevin Singh

Maximiliano Hernández as Mr. Robineau

Darby Stanchfield as Gloria Borlock

Giancarlo Esposito as Archie Brubaker

Collin Blackford as Benny Burrito

Annacheska Brown as Tess Reed

Shelby Simmons as Hillari Kimble

Allison Wentworth as Dori Dilson

Juliocesar Chavez as Alan Ferko

Artemis as Mallory Franklin

Julia Flores as Summer

Gabriella Surodjawan as Kim

John Apolinar as Wayne Parnell

Alex James as Zack James

Enzo De Angelis as Leo Age 8

Cayman Guay as Cool Girl

Sara Arrington as Ana Caraway

Lucinda Marker as Principal Sutters

Hannah Kauffmann as Band Leader

Gavin White as Big Kid #1

Sean Dennis as Big Kid #2

David Trujillo as Big Kid #3

Troy Brookins as Ron Kovac

Ryan Begay as Mud Frog Fan

Damian O'Hare as Leo's Dad

Audra Charity as Emcee

Atharva Verma as Kevin Age 8

Jimmy E. Jones as Teacher

Orion Carrington as Young Male Teacher

Tom Sons as EMT

Eric Archuleta as Athletic Trainer

Rebecca Ann Arscott as Keyboard Player: Winter Dance Band

Herve Gaspard as Lead Singer / Guitar: Winter Dance Band

Paul Palmer III as Drummer: Winter Dance Band

Artha Meadors as Bass: Winter Dance Band

Armando Arellano as Mudfrogs Marching Band

Victor Armijo as Mudfrogs Marching Band

Andrew Blair as Mudfrogs Marching Band

Vincent Conte as Mudfrogs Marching Band

Giselle Gruz as Mudfrogs Marching Band

Oscar Gamboa as Mudfrogs Marching Band

Edgar Hernandez as Mudfrogs Marching Band

Gabe Hicks as Mudfrogs Marching Band

Chris Kingswadd as Mudfrogs Marching Band

Shannon Latham as Mudfrogs Marching Band

Julio Quiroz Lopez as Mudfrogs Marching Band

Spenser Lotz as Mudfrogs Marching Band

Gus Pedrotty as Mudfrogs Marching Band

Isiah Rojas as Mudfrogs Marching Band

Alla Shapiro as Mudfrogs Marching Band

Jeanette Silva as Mudfrogs Marching Band

Kayla Strickler as Mudfrogs Marching Band

David Hight as Speech Competition Attendee / Ball Game Attendee (uncredited)

Jesse Mattson as Football Player (uncredited)

J. Nathan Simmons as Fan (uncredited)

Michael E. Stogner as Fan (uncredited)

Ian Willoughby as Football Player (uncredited)

Shylo Molina as Talent Show Magician (uncredited)

Alexander Alayon Jr. as High Schooler (uncredited)

Braden Wilcox as High School Student (uncredited)