Mary is a ten-year-old orphan sent from India to live at Misselthwaite Manor in Yorkshire. Raised by servants who yielded to her every demand to keep her quiet, she arrives in England with a sour disposition and zero independence. She finds the massive, gloomy estate lonely and initially treats the staff with the same demanding attitude she used in India.

Dickon is a twelve-year-old local boy who spends his days wandering the Yorkshire moors. He possesses an unusual affinity for wild animals and plant life, understanding nature in a way that feels almost magical to city dwellers. He serves as a gentle guide for Mary as she learns about gardening and the local environment.

Colin is the ten-year-old son of Archibald Craven, living a highly restricted life inside Misselthwaite Manor. Convinced by the adults around him that he is deathly ill and will develop a curved spine, he refuses to leave his bed or let people look at him. His isolation has made him demanding and prone to severe hysterical fits when denied his way.

Archibald Craven is the master of Misselthwaite Manor, a wealthy man defined by a decade of intense mourning. He has a slight physical curvature of the spine and spends most of his time traveling across Europe to avoid the memories housed within his estate. He provides for his son and niece financially but remains entirely detached from their daily lives.

Martha is a young housemaid at Misselthwaite Manor and a member of a large, boisterous family from the nearby moor. She speaks in a thick Yorkshire dialect and refuses to coddle Mary the way the servants in India did. Her cheerful, practical attitude provides Mary with her first model of functional independence.

Mrs. Medlock is the stout, strict housekeeper of Misselthwaite Manor. She runs the massive, 600-year-old estate with rigid efficiency while Mr. Craven is away traveling. She views children as an inconvenience and expects Mary to remain unseen and out of trouble.

Ben is an elderly, weather-beaten gardener who has worked at Misselthwaite Manor for many years. He prefers the company of plants and birds over people, displaying a crusty and irritable exterior. Despite his gruffness, he maintains a soft spot for the estate's resident robin.

Susan Sowerby is a mother of twelve living in a small cottage on the Yorkshire moor. Though she has little money, she possesses vast common sense and a warm, nurturing spirit. The adults at Misselthwaite Manor frequently seek her practical advice regarding the children's welfare.

The Robin is a friendly European bird living on the grounds of Misselthwaite Manor. Having been a lonely fledgling himself, he seeks out companionship. He flits around the estate gardens, providing Mary with her first sense of welcome in a strange new place.

Lilias Craven is the late wife of Archibald Craven and the mother of Colin. She died ten years prior to the story's events following an accident involving a falling tree branch. Her memory casts a long shadow over Misselthwaite Manor, dictating the locked doors and sorrowful atmosphere of the estate.

Doctor Craven is Archibald's brother and the resident physician for his nephew Colin. He continuously reinforces Colin's fears about illness, insisting on bed rest and isolation. He manages the boy's health with a cautious, pessimistic approach.