Nicholas is a handsome, gentlemanly young man thrust into sudden poverty. Barely an adult, he is desperate to provide for his widowed mother and sister, leading him to accept a harsh teaching position at a Yorkshire boarding school despite his misgivings. He possesses a strong ethical code, prioritizing compassion and justice over personal safety or financial gain.

Ralph is Nicholas's wealthy and estranged uncle, a ruthless London businessman with little compassion for those without capital. He isolates himself with his wealth and views his deceased brother's family as a nuisance. Rather than offering genuine support, he uses his connections to place his nephew and niece in difficult, vulnerable positions while pursuing his own financial interests.

Kate is Nicholas's beautiful and devoted sister. Raised in comfortable circumstances, she is forced into the working world to help support her family. Despite the vulnerability of her position as an impoverished young woman in a patriarchal society, she maintains high moral standards and insists on making an honest living while enduring workplace hostilities and unwanted attention.

Mrs. Nickleby is the recently widowed mother of Nicholas and Kate. Ashamed of her family's new financial ruin, she is somewhat naive and easily influenced by wealthy or powerful men. Her deference to status sometimes clouds her judgment, leading her to misread the intentions of the men who surround her vulnerable daughter.

Mr. Squeers is the sinister, one-eyed headmaster of Dotheboys Hall. He profits by taking in vulnerable children for a cheap tuition, only to severely neglect and abuse them while his own family lives comfortably. He views his pupils as enemies and sources of income, utilizing his authority to terrorize those unable to defend themselves.

Smike is a young man who has lived at Mr. Squeers's boarding school since childhood, suffering years of physical and emotional abuse. He has no memories of a family or a happy past. Broken by his environment, he functions as an overworked and underfed servant until Nicholas's arrival gives him his first real experience of kindness.

Newman Noggs is Ralph Nickleby's clerk, a former gentleman who fell into debt and indenture to Ralph. Despite his pitiable salary and unkempt appearance, he retains a strong moral compass. Aware of his employer's corrupt business practices, Newman quietly acts as a secret ally to Nicholas and his family, risking his own meager livelihood in the process.

Charles Cheeryble is a wealthy, older businessman who runs a successful firm alongside his brother Ned. Remembering his own impoverished roots, he is exceptionally generous and uses his wealth to help others. He operates his business with strong morals and a cheerful disposition, providing a sharp contrast to the predatory practices of men like Ralph Nickleby.

Madeline is a beautiful, financially struggling young woman who devotes herself to caring for her impoverished and sick father. Supported secretly by the Cheeryble brothers, she feels bound by duty to her father, making her vulnerable to predatory men who view marriage to her as a lucrative business transaction.

Sir Mulberry Hawk is a wealthy, dissipation-prone gentleman who lives entirely for his own pleasure. Accustomed to taking what he wants without consequence, he aggressively pursues Kate Nickleby. He operates with a sense of entitlement granted by his social status, treating women as objects for his amusement.

Fanny is Mr. Squeers's 23-year-old unmarried daughter. She lives a privileged life compared to the boys at the school and enjoys inventing frivolous dramas. She quickly develops an infatuation with Nicholas, constructing imaginary scenarios about their courtship that clash with his complete lack of interest.

John Browdie is a jovial, loud Yorkshire man engaged to Fanny Squeers's best friend. Despite an initially awkward introduction to Nicholas, he proves to be a generous and practical local who appreciates Nicholas's defense of the abused students at Dotheboys Hall.

Miss La Creevy is a miniature-portrait painter and the Nickleby family's landlord in London. A talkative but genuinely kind woman, she offers the Nickleby women emotional support and practical assistance as they attempt to survive their sudden poverty and London's dangerous social dynamics.

Arthur Gride is an elderly, greedy associate of Ralph Nickleby. He combines economic and sexual exploitation, utilizing a family's debt to try and purchase a much younger bride. He operates entirely out of self-interest, viewing marriage strictly as a path to accumulating more wealth.

Mr. Crummles is a theatrical manager who runs a traveling acting troupe. He takes an immediate liking to Nicholas and generously offers him and Smike paid work. His theatrical world, while eccentric, provides a welcoming and hospitable refuge for the runaway pair.

Madame Mantalini is a dressmaker and milliner in London who hires Kate Nickleby. She runs a demanding business but is constantly plagued by the reckless spending and flirtations of her husband, which threaten to drive her shop into bankruptcy.