The titular protagonist, Oliver Twist is orphaned at birth and brought up by the parish under circumstances that amount to child abuse. Despite his ill treatment, Oliver is a kind, honest boy who is quick to forgive. He is motivated by the desire to help those in need and by gratitude to those who help him. Despite the abuse he receives at others' hands, he never holds a grudge and is always ready to give a person the benefit of the doubt. At the back of Oliver's mind is the desire to learn more about his mother. As a child he thinks about her watching over him and feels deeply that she must have been a good person. It is her nature that Oliver has inherited, and no matter how much abuse and manipulation he experiences, he remains true to his nature. In the end Oliver gathers around him a group of honest, kindhearted friends similar to himself.
An old man with an ugly face and matted red hair, Fagin is a sort of criminal mastermind. He fences stolen goods, taking a large cut for himself. He looks and lives like a pauper, but he has plenty of money. He even owns more than one house. Readers meet Fagin in his public persona of a jolly old fellow taking care of his young charges, but the boys with him are really apprentice thieves. Fagin is a corrupter of the young, and Dickens often refers to him as the devil. Fagin demands total compliance and does not hesitate about turning in to the police anyone who crosses him or whom he perceives as a threat. That way the police will do his dirty work for him by sending his enemies to the gallows. Fagin may seem charming, but he's as evil as they come—the antithesis of Oliver Twist.
If anyone resembles Oliver's mother in character, it's Rose Maylie. Like Oliver she was orphaned as a child. She was then raised by abusive foster parents. When Mrs. Maylie found Rose, she was a ragged child, underfed and unloved. Mrs. Maylie took her in and raised her as her niece. Rose is young but very caring and maternal. She puts the needs of others before her own. When Harry Maylie proposes, for instance, she turns him down because she fears her origins would ruin his reputation and thus his career. Like the ideal mother, Rose nourishes Oliver with food, knowledge, and love.
Mr. Brownlow is a gentleman through and through. When Jack steals his handkerchief and Oliver is accused of it, Mr. Brownlow doesn't assume Oliver's guilt, and in fact, he feels more concern about Oliver's well-being than about his own loss. Mr. Brownlow is generous and impetuous. He takes Oliver, who is a stranger and possibly a criminal, into his home and nurses him. However, when Oliver doesn't return from an errand, Mr. Brownlow is quick to believe that the boy may have robbed him. Still his good heart wins out. As a born scholar, he doggedly researches Oliver's identity.
Nancy came to Fagin when she was just a few years old, and he trained her well. Although never stated in the novel, Dickens says in his preface to the third edition that Nancy practices prostitution to make a living. She also deeply loves the burglar Bill Sikes. Despite her upbringing, Nancy shows as much compassion and love as Rose Maylie. She takes to Oliver from the start and wants to save him from a life on the streets. Her commitment to protecting both Oliver and the people she considers her family (Bill and Fagin's boys) ultimately prompts her to sacrifice herself for them.
Bill Sikes, an experienced housebreaker (burglar), takes his loot to Fagin to fence. Fagin values Sikes's skills as a meticulous planner and a reliable partner in crime. Sikes lives with Nancy and his dog, Bull's-eye. Bill Sikes is a bit of an enigma. He shows little humanity in his words, but some of his actions, such as his care of Oliver after the boy is shot, might indicate that his habitual surliness is in part a defensive posture. In the preface to the third edition, Dickens seems to suspect that Sikes's "gentler human feeling" is simply hard to find. He is the only character in the novel with a pet and is often indulgent of Nancy when she violently disagrees with him. After killing her when his temper gets the better of him, he is almost completely incapacitated by guilt.
As parish beadle Mr. Bumble acts as a liaison between the church, the workhouse, the baby farm, and other organizations for looking after the poor of the parish. He views himself as important and influential and resents any questioning of his authority. Ultimately he gets his comeuppance in his marriage and ensuing fall from power. Dickens uses Mr. Bumble to illustrate the inadequacy of the poor laws and the hypocrisy of those who "care for" the poor, often putting words in his mouth that highlight the neglect inherent in this "care."