Fright Nights, a company which specialises in ghost hunts, will be holding paranormal investigations on August 4 and 25.
People will be allowed to spend the night at the castle, visiting the Ghost Tower between 9pm and 5am where they will be part of an overnight ghost hunt using the latest psychic equipment.
There are more than 400 years of reported paranormal activity at the castle.
The earliest spirit is said to be that of Moll Bloxham, a witch who cursed the castle with the ghost of a savage dog. Town vicars tried to exorcise it but four centuries on, it is still said that the dog can be seen wandering along the ramparts.
Spokeswoman Jo Biggs said: "Many visitors have heard mysterious footsteps pacing the corridors of the castle. The ghost of Sir Fulke Greville, the poet and statesman, still haunts the tower where he lived before he was stabbed to death by his servant during an argument over money."
Fright Nights is also offering a ghost tour of the castle on Friday July 21 from 7pm including a vigil in the dungeon with a clairvoyant.
Call 620028 for details.