Mary is a 23-year-old woman who grew up on a peaceful farm in the southern town of Helford. Following the death of her mother, she honors her dying wish by moving to the harsh moorlands to live with her only surviving relative. She is highly independent and resilient. Holding pragmatic views about romance, she prefers logic over sentimentality, and her natural courage frequently places her at odds with the violent men surrounding her new home.

Joss is the landlord of the isolated Jamaica Inn and the husband of Aunt Patience. Standing nearly seven feet tall, he uses his massive size and terrifying temper to govern his household through fear. He suffers from a severe addiction to alcohol that triggers paranoid episodes. Despite his brutish exterior, he possesses surprisingly dexterous hands and manages an illicit nighttime operation out of his property.

Jem is Joss's younger brother and a self-proclaimed horse thief living near Kilmar Tor. He shares the dark physical traits of the Merlyn family, including a distinctly cruel shape to his mouth. Despite his rough upbringing and criminal livelihood, he possesses a roguish honesty. He frequently warns Mary to leave the dangerous environment of the inn.

Patience is Mary's maternal aunt and Joss Merlyn's wife. Once remembered by Mary as a lovely, vivacious woman, years of living with her tyrannical husband have completely shattered her spirit. She is now a terrified woman who suffers from a nervous tic of constantly working her mouth. She inexplicably attempts to cover up her husband's illicit activities and protect him.

Francis Davey is the Vicar of Altarnun, living a quiet and solitary life in a parish near the moors. He has albinism, characterized by pale skin, white hair, and striking white eyes. The vicar maintains a deep fascination with the ancient, pre-Christian history of the Cornish region. He quickly positions himself as a calm, educated confidant for Mary when she needs an escape from the inn.

Squire Bassat is the local magistrate and justice of the peace for the area. He previously owned the inn before selling it to the Merlyn family. Bassat represents the only nearby law enforcement actively attempting to crack down on the smuggling activity occurring in the region. His blunt methods often leave him frustrated by the cunning of the local criminals.

Harry is a pedlar and a regular fixture among the rough crowd that frequents the inn under the cover of darkness. He is an opportunistic, deeply cruel man who actively participates in the illicit nighttime activities organized on the property. His willingness to torment vulnerable people makes him a particularly repulsive figure.

Mrs. Yellan was Mary's mother and Patience's sister. After her husband died, the constant strain of managing their failing farm eventually caused her health to decline permanently. Her dying wish forces Mary to leave her childhood home and seek out her estranged aunt.

Matthew was the older brother of Jem and brother to Joss. Like the other men in his family, he lived a rough life that ended violently. He died young by drowning in the treacherous bogs of the moor, adding to the local legends about his family's bad blood.

Mrs. Bassat is the wealthy, respectable wife of the local magistrate. She frequently finds herself unwittingly caught up in local mischief, such as when she visits the Launceston market to replace a stolen horse and accidentally buys the exact animal back.

Richards is a loyal servant employed by the Bassat household. He assists the magistrate's family with their errands and transportation. He provides practical support and a reassuring presence when the household becomes entangled with the affairs of the inn.