A list of characters who appear in the Wizard's Castle books.
- Annabel Fairfax - An old school friend of Fanny's and a talented witch trained by Mrs. Pentstemmon. She took Martha as an apprentice, but didn't mind when Martha and Lettie switched.
- Ben Sullivan - Royal Wizard of Ingary and known there as Wizard Suliman. Originally from Wales, like Howl. He disappeared trying to get rid of the Witch of the Waste.
- Calcifer - Howl's fire demon who powers the Moving Castle. He had a contract with Howl in the first book that was doing neither of them any good.
- Fanny Hatter - Mr. Hatter's second wife, stepmother to Sophie and Lettie and mother of Martha. After her husband's death, she took advantage of Sophie's sewing skills and kept her in the shop all day making hats.
- Howell Jenkins - The Wizard Howl, originally from Wales, England. An unscrupulous, talented wizard rumored to eat girls' hearts. He is vain, ostentatious, and "hates being pinned down to anything." Known as the Wizard Jenkin in Porthaven and the Wizard Pendragon in Kingsbury.
- The King of Ingary - Contracted Howl to make spells for him, then later made him Royal Wizard after Wizard Suliman disappeared. His name is never given.
- Lettie Hatter - The middle Hatter daughter. Apprenticed at Cesari's Bakery after her father's death, but switched places with her sister Martha because she wanted to be learned and famous. Later married Ben Sullivan and had one daughter.
- Prince Justin - Brother of the king of Ingary. He and his brother quarrel frequently. Prince Justin disappeared looking for Wizard Suliman, then again later for Princess Beatrice of Strangia.
- Martha Hatter - The youngest Hatter girl. Apprenticed to a witch after her father's death, but switched places with her sister Lettie because she wanted to marry young and have ten children. Promised to Michael.
- Michael Fisher - Howl's apprentice, a nice, polite boy. Orphaned in Porthaven, where his parents were poor fishers. He became Howl's apprentice when he took to sleeping on his doorstep. He met Martha at Cesari's and fell in love with her, and is waiting until both their apprenticeships are finished so he can marry her.
- Morgan Pendragon - Howl and Sophie's young son, who was born when Howl had turned Sophie into a cat.
- Mrs. Penstemmon - An imposing, influential woman whose fortunes are known to never be wrong. She trained many famous and powerful witches and wizards, including Matilda Regis, Annabel Fairfax, Ben Sullivan, and Howell Jenkins. The Witch of the Waste killed her when she refused to reveal Howl's location.
- Percival - A man cursed by the Witch of the Waste, turning him into a dog. He was taken in by Lettie, who fell in love with him. In truth, the Witch of the Waste created him from Wizard Suliman's and Prince Justin's "spare parts."
- Sophie Hatter - The eldest of the three Hatter sisters, who believed she was doomed to failure because of her position in the family. She remained in the hat shop after her father's death, where she spent all day shut up making hats. When the Witch of the Waste cursed her, turning her into an old woman, she left home to seek her fortune and found it in Howl's Castle. Later married to Howl with one son, Morgan.
- Princess Valeria - The royal princess of Ingary, only a toddler in Howl's Moving Castle and a young girl prone to tantrums in Castle in the Air.
- Witch of the Waste - An infamous, evil witch who was exiled to the Waste fifty years ago by the king. She threatened the king's daughter, so he sent Wizard Suliman to deal with her, but she got to him. She and Howl used to be in a relationship, but he jilted her, so she placed a curse on him.
- Adolphus Rex Norlandi Alti - King Adolphus X of High Norland. An elderly man who is devoted to working in his library.
- Charmain Baker - A young girl from a well-to-do family that keeps a bakery in the capital of High Norland. Because of her mother's obsession with respectability, Charmain was raised without learning the most basic household skills. A devout bookworm, Charmain's greatest dream is to work in the royal library, but she was called on to house-sit for her Great-Uncle William, the Wizard Norland, when he was ill and taken to be cured by the elves.
- Princess Hilda - The eldery daughter of King Adolphus. She turned down all marriage proposals and is devoted to working in her father's library.
- Lubbock - A frightening, bug-like creature from the mountains in High Norland. Lubbocks reproduce by sticking an appendage into a human and laying eggs. The first egg to hatch eats all the others, then eats its way out of the host if he is male, or is given birth to normally if the host is female. Lubbock offspring born from human women are called lubbockin and look almost entirely human, except with purple eyes or a purplish tint to the skin.
- Wizard Norland - The Royal Wizard of High Norland and Charmain's distant relation, known to her as Great-Uncle William. He fell ill and was taken by elves to be cured.
- Matilda Regis - The Witch of Montalbino. A very efficient woman.
- Peter Regis - Matilda Regis's son. An inept young wizard sent by his mother to Wizard Norland to learn magic.
- Princess Beatrice - The crown princess of Strangia, kidnapped in Castle in the Air by the djinn Hasruel. She is a straightforward, no-nonsense person.
- Gareth - Megan's husband and Howl's brother-in-law.
- Lily Angorian - Neil's English teacher; claims to be Ben Sullivan's fiancée, but is really the Witch of the Waste's fire demon. Howl pretends to court her.
- Megan - Howl's sister, who is constantly nagging him for not being "respectable."
- Mari - Megan's daughter; adores her uncle Howl.
- Neil - Megan's son, a bratty young boy with a smart mouth.
- Abdullah - A carpet merchant from Zanzib who has a poor relationship with his father's family. He bought a magic carpet from a traveller, which took him to the garden of his dreams, where he met the woman of his dreams, Flower-in-the-Night. A prophecy made at his birth said that one day the sultan of Zanzib would "raise him higher than anyone in the land."
- Dalzel - A djinn born of a good djinn but fathered by an evil djinn. No female djinn would marry a half-breed like him, so he gave into his evil side and enslaved his brother Hasruel, forcing him to kidnap all the princesses in the world to be his wives.
- Flower-in-the-Night - The daughter of the sultan of Zanzib who was raised in seclusion because of a prophecy made at her birth stating she would fall in love with the first man she saw aside from her father. Abdullah wound up being that first man when his magic carpet brought him to her garden. She was then kidnapped by the djinn Hasruel, spurring Abdullah to rescue her.
- Hasruel - A good djinn enslaved by his younger brother Dalzel, who took Hasruel's "life" and hid it.
- Jamal - A cook who sold food next to the stall where Abdullah sold his carpets. He and Abdullah became great friends.