Jared Grace / Simon Grace
Mallory Grace
Arthur Spiderwick
Helen Grace
Mulgarath
Aunt Lucinda Spiderwick
Richard Grace
Hogsqueal (voice)
Thimbletack (voice)
Young Lucinda Spiderwick
Mrs. Spiderwick
Helen's Co-Worker
Nurse
Tow Truck Driver
Additional Performer
Red Cap (voice) (uncredited)