Mary is a teenage girl living in Manchester who becomes an apprentice to a dressmaker after her mother's death. She dreams of achieving a better life and elevating her social status, often imagining that she will eventually become a wealthy lady. She is caught between two very different suitors: the affluent mill owner's son Harry Carson and her childhood friend Jem Wilson.

John is a proud, working-class mill worker who is fiercely devoted to his daughter Mary following the early death of his wife. He holds a deep resentment toward the wealthy mill owners, believing they actively exploit the working class and ignore their suffering. As he struggles with poverty, he becomes heavily involved in the radical Chartist movement and local trades' unions.

Jem is the son of George and Jane Wilson who works steadily as a mechanical engineer. He harbors a deep and persistent love for Mary Barton, though she initially rejects his advances. He is a hardworking and honorable young man who supports his mother and takes his responsibilities to his family seriously.

Harry is the wealthy, handsome son of the mill owner John Carson. He takes a strong interest in Mary Barton, using a go-between to arrange secret meetings with her. His affluent background gives him a sense of entitlement, and he views the working-class people employed by his father with disdain.

John is a highly successful mill owner in Manchester who originally comes from a working-class background. Despite his humble beginnings, he has grown disconnected from the realities of poverty and largely ignores the suffering of his employees. He focuses on protecting his business interests during economic downturns, maintaining a comfortable lifestyle for his family while his workers starve.

George is a mill worker and the best friend of John Barton. He is more empathetic and less radical than John, attempting to see the perspective of the mill owners even during difficult economic times. He works tirelessly to support his family and goes out of his way to help neighbors in desperate need.

Jane is George Wilson's wife and Jem's mother. She suffered a permanent injury while working at a cotton mill before her marriage, which affects her physically and emotionally. She is deeply attached to her son Jem and is highly protective of him, often viewing Mary Barton's treatment of him with frustration.

Margaret is a young seamstress who quickly becomes a close friend and moral influence on Mary Barton. She lives with her grandfather, Job Legh, and works hard to support them both. As her eyesight begins to fail, threatening her livelihood, she discovers that she has a talent for singing that might allow her to earn a living.

Job is Margaret Jennings's grandfather and a highly intelligent working-class man with a keen interest in science. He raised Margaret alone after the sudden death of his daughter. Though he works in the mills and participates in the union, he prefers sensible debate over the extremism favored by men like John Barton.

Esther is Mary Barton's aunt who ran away from home after earning money as a factory worker. Her sudden disappearance causes immense distress to her sister, Mary Barton Sr. She dreams of one day returning to make her niece Mary into a lady, though her choices lead her into severe poverty and hardship on the streets of Manchester.

Alice is George Wilson's sister who works as a nurse in Manchester. She is a kind-hearted woman who often reminisces about her early life in the north and dreams of returning there, though poverty and her duties keep her in the city. She raised her nephew Will and serves as a comforting presence to her neighbors.

Will is Alice Wilson's nephew, whom she raised from a young age. He works as a sailor who spends most of his time at sea, returning to Manchester occasionally to visit his family. He quickly becomes captivated by Margaret Jennings after hearing her sing.

Mary Sr. is John Barton's wife and Mary Barton's mother. She is deeply affected by the disappearance of her sister Esther and still mourns the death of her young son Tom. Her fragile health and nervous state set the stage for the family's subsequent struggles.

Sally is a working-class acquaintance of Mary who acts as a secret messenger between Mary and Harry Carson. She encourages Mary's relationship with the wealthy man, not fully understanding the danger or Mary's internal conflicts regarding the romance.

Miss Simmonds runs a dressmaking business in Manchester and employs Mary Barton. She represents the respectable working-class trade that John Barton selects for his daughter to keep her out of the factories and away from upper-class households.

Davenport is a mill worker employed by the Carsons who falls sick with a severe fever. His extreme poverty and the squalid conditions of his family's home illustrate the desperate realities faced by Manchester's working class during the economic downturn.