Casey Kasem as Shaggy Rogers / Mirror Monster (voice)

Don Messick as Scooby-Doo / Scrappy-Doo (voice)

Glynis Johns as Ms. Grimwood (voice)

Susan Blu as Sibella Dracula (voice)

Patty Maloney as Tanis the Mummy (voice)

Pat Musick as Elsa Frankensteen (voice)

Marilyn Schreffler as Winnie Werewolf (voice)

Russi Taylor as Phantasma (voice)

Frank Welker as Matches / Papa Werewolf / Well Dweller (voice)

Andre Stojka as The Grim Creeper / Mummy Daddy (voice)

Zale Kessler as Daddy Dracula / Frankenstein Senior (voice)

Hamilton Camp as Phantom Father (voice)

Ruta Lee as Revolta (voice)

Ronnie Schell as Colonel Calloway (voice)

Scott Menville as Cadet Tug Roper (voice)

Aaron Lohr as Cadet Miguel (voice)

Bumper Robinson as Cadet Jamaal (voice)

Remy Auberjonois as Cadet Baxter (voice)

Jeff Cohen as Cadet Grunt (voice)

Brian Cummings as Fan Monster (uncredited voice)

Linda Gary as Doorbell Monster (uncredited voice)