Joey King as Wren

Julia Goldani Telles as Hallie

Jaz Sinclair as Chloe

Annalise Basso as Katie

Alex Fitzalan as Tom

Taylor Richardson as Lizzie

Javier Botet as Slender Man

Jessica Blank as Hallie's Mom

Michael Reilly Burke as Hallie's Dad

Kevin Chapman as Mr. Jensen

Miguel Nascimento as Kyle

Eddie Frateschi as Biology Teacher

Oscar Wahlberg as Boy with Glasses

Danny Beaton as Burley Kid

Marc Carver as Doctor

Kris Sidberry as Librarian

Angela Hope Smith as Nurse

Damon D'Amico Jr. as Student

Timothy Brierley as Tour Guide

Kayla Caulfield as High School Student (uncredited)

Jeffrey Corazzini as Police Officer (uncredited)

Michael Tow as Calculus Teacher (uncredited)

Adrian M. Mompoint as Jock (uncredited)

Kieran Tuomey as Student (uncredited)

Gabrielle Lorthe as Cheerleader (uncredited)

Yohanna Perez as Student (uncredited)