Will Forte as Shaggy Rogers (voice)

Frank Welker as Scooby-Doo / Pterodactyl (voice)

Mark Wahlberg as Blue Falcon (voice)

Jason Isaacs as Dick Dastardly (voice)

Ken Jeong as Dynomutt, Dog Wonder (voice)

Amanda Seyfried as Daphne Blake (voice)

Gina Rodriguez as Velma Dinkley (voice)

Zac Efron as Fred Jones (voice)

Iain Armitage as Young Shaggy (voice)

Ariana Greenblatt as Young Velma (voice)

Mckenna Grace as Young Daphne (voice)

Pierce Gagnon as Young Fred (voice)

Kiersey Clemons as Dee Dee Skyes (voice)

Tracy Morgan as Captain Caveman (voice)

Simon Cowell as Simon Cowell (voice)

Harry Perry as Harry Perry (voice)

Kevin Heffernan as Bike Cop Gary (voice)

Christina Hendricks as Officer Jaffe (voice)

Henry Winkler as Keith (voice)

John DiMaggio as Restaurant Owner (voice)

Ira Glass as Ira Glass (voice)

Henry Kaufman as Chad / Chet (voice)

Maya Erskine as Judy Takamoto (voice)

Billy West as Muttley (voice)

Don Messick as Muttley (archive sound) (voice)

Fred Tatasciore as Cerberus (voice)

Kennedy Peil as Indira Knight (voice)

John McDaniel as Hal Murphy (voice)

Ryan Folsey as Beach Guy (voice)

Justina Machado as Jamie Rivera (voice)

Pam Coats as Mrs. Rogers (voice)

Tony Cervone as Ghost / Mr. Rigby / Alice (voice)

Alex Kauffman as Officer North (voice)

Vanara Taing as Baby Rotten (voice)

Sarah Lancia as Dispatcher Stevens (voice)

Eric Cowell as Ben (voice)

Maven Morgan as Kari (voice)

Adam Sztykiel as Officer Casey (voice)

Michael Kurinsky as Samuel Colton (voice)