The book is divided into five chapters, which Dickens titled "staves".
A Christmas Carol opens on a bleak, cold Christmas Eve in London, seven years after the death of Ebenezer Scrooge's business partner, Jacob Marley. Scrooge, an ageing miser, dislikes Christmas and refuses a dinner invitation from his nephew Fred—the son of Fan, Scrooge's dead sister. He turns away two men who seek a donation from him to provide food and heating for the poor and only grudgingly allows his overworked, underpaid clerk, Bob Cratchit, Christmas Day off with pay to conform to the social custom.
That night Scrooge is visited at home by Marley's ghost, who for the past seven years has been doomed to wander the Earth, entwined by heavy chains and money boxes forged during a lifetime of greed and selfishness, and now regrets ignoring the needs of his fellowmen in life, but is too late to ever make amends for his actions. Marley tells Scrooge that he has a single chance to avoid the same fate: he will be visited by three spirits and must take heed, or else be cursed to carry much heavier chains of his own.
The first spirit, the Ghost of Christmas Past, takes Scrooge to Christmas scenes of Scrooge's boyhood, reminding him of a time when he was more innocent. The scenes reveal Scrooge's lonely childhood at boarding school, his relationship with his beloved sister Fan, and a Christmas party hosted by his first employer, Mr Fezziwig, who treated him like a son. Scrooge's neglected fiancée Belle is shown ending their relationship, as she realises that he will never love her as much as he loves money. Finally, they visit a now-married Belle with her large, happy family on the Christmas Eve that Marley died. Scrooge, upset by hearing Belle's description of the man that he has become, demands that the ghost remove him from the house.
The second spirit, the Ghost of Christmas Present, takes Scrooge to a joyous market with people buying the makings of Christmas dinner and to celebrations of Christmas in a miner's cottage and in a lighthouse. Scrooge and the ghost also visit Fred's Christmas party. A major part of this stave is taken up with Bob Cratchit's family feast and introduces his youngest son, Tiny Tim, a happy boy who is seriously ill. The spirit informs Scrooge that Tiny Tim will die unless the course of events changes. Before disappearing, the spirit shows Scrooge two hideous, emaciated children named Ignorance and Want. He tells Scrooge to beware the former above all, for they will doom anyone who attempts to ignore them, and mocks Scrooge's concern for their welfare.
The third spirit, the Ghost of Christmas Yet to Come, shows Scrooge a Christmas Day in the future. The silent ghost reveals scenes involving the death of a disliked man whose funeral is attended by local businessmen only on condition that lunch is provided. His charwoman, laundress and the local undertaker steal his possessions to sell to a fence. When he asks the spirit to show a single person who feels emotion over his death, he is only given the pleasure of a poor couple who rejoice that his death gives them more time to put their finances in order. When Scrooge asks to see tenderness connected with any death, the ghost shows him Bob Cratchit and his family mourning the death of Tiny Tim. The ghost then allows Scrooge to see a neglected grave, with a tombstone bearing Scrooge's name. Sobbing, Scrooge pledges to change his ways.
Scrooge awakens on Christmas morning a changed man. He makes a large donation to the charity he rejected the previous day, anonymously sends a large turkey to the Cratchit home for Christmas dinner and spends the afternoon with Fred's family. The following day he gives Cratchit an increase in pay, and becomes a father figure to Tiny Tim. From then on Scrooge treats everyone with kindness, generosity and compassion, embodying the spirit of Christmas.