Fifty-seven-year-old Landon Carter narrates the novel, reflecting on events from 40 years in the past. The novel opens with a Prologue, in which the older Landon, living in the same North Carolina town as he did at the age of 17, stands near the Baptist church that figures prominently in the novel and gets himself in the mindset of his 17-year-old self. The story begins in 1958 and is, Landon tells us, both joyful and sad.
Seventeen-year-old Landon is a senior at Beaufort High School, which collaborates each year with Southern Baptist Church on a Christmas play called The Christmas Angel. The play, written by Reverend Hegbert Sullivan, the minister of the church, tells the story of a man who is so grief-stricken over the death of his wife (while giving birth to their only child) that he is not much of a father to his child. An angel appears to the man, and she admonishes him to be a better father; she also performs a small miracle for the family on Christmas morning. The popular play, performed in the local playhouse, features seniors from the high school.
Landon's father is a congressman who spends most of his life in Washington, D.C., and is a stranger to his son. Landon's grandfather, who is now deceased, was a bootlegger and banker during the Great Depression, and he built the Carter family fortune by preying on the poor. One of Grandfather Carter's employees was Reverend Sullivan, who still harbors resentments against the Carters.
Like the narrative of The Christmas Angel, Reverend Sullivan's wife died during childbirth, and he has raised his daughter, Jamie, on his own. Jamie and her father are deeply connected, but Jamie is ostracized by her classmates because of her religious devotion, unflattering clothing and hairstyle, and tendency to help the downtrodden. Although Landon has known Jamie most of his life — as classmates and fellow church members only — he is surprised to notice at the beginning of his senior year that she is becoming a woman and could almost be considered attractive.
Early in his senior year, Landon is elected student body president and must attend the upcoming Homecoming Dance. Mortified by the idea of attending without a date, Landon invites Jamie, who dresses nicely and does not carry the Bible she usually always has with her. The evening ends eventfully when Jamie and Landon find themselves cleaning up after and taking care of Landon's former girlfriend, who has gotten drunk.
Some weeks later, Jamie asks Landon to play the part of the father in the Christmas play; she has already been cast as the angel. Landon reluctantly agrees. The two begin spending time together — although Landon does so only out of obligation — but in the course of their conversations, Landon discovers that Jamie's only goal in life is to get married with a church full of people in attendance, an unlikely occurrence given Jamie's social status. Landon finds this goal odd for such an excellent student as Jamie, who could have far loftier aspirations; he is especially surprised that she does not plan to attend college.
Landon visits an orphanage with Jamie and sees one of her pet projects firsthand. However, all their togetherness is frustrating for Landon, and he bursts out angrily at Jamie the night before the play performance, telling her he hasn't enjoyed any of their time together. Jamie is visibly hurt. Landon apologizes the next evening and, for reasons inexplicable to him, holds her hand during the apology.
The play is a great success, and in a pivotal scene, in which the father is supposed to notice the ravishing beauty of the angel, Landon is shocked by how beautiful Jamie looks in her white dress; she is wearing a touch of makeup and has taken her long hair out of a bun and let it fall past her shoulders. The other students in the school are as surprised by Jamie's appearance as Landon is, but her upgraded social status does not last, and Jamie is soon relegated to her former social status.
Jamie asks Landon to help her collect the bottles and cans she set out in a donation drive to buy presents for the orphans. Astonished by the paltry donations, Landon empties his own bank account and adds those funds to the collection without telling anyone what he has done. With this decision to help Jamie and the orphans in this way, Landon surprises himself.
Jamie buys gifts for the orphans and invites Landon to the orphanage Christmas party; while there, Landon is deeply touched by both the starkness of the orphan's surroundings and by the deep connection Jamie shares with the young orphans. He is also surprised by how beautiful she looks; he cannot take his eyes off her. Landon soon realizes he has fallen in love with Jamie.
Landon invites Jamie to eat Christmas dinner at his family's historic and beautiful mansion; afterward, he asks Jamie whether he can begin seeing her regularly. She agrees. The next day, they kiss for the first time, and the two begin dating. Landon notices, however, that Jamie is often fatigued and cold, and even has some bruising on her body. When Landon tells Jamie that he loves her, she realizes that she must tell him her stunning news: She is dying of a rare form of leukemia and has only a few months to live. Landon is devastated, but he works through his fear and sadness and begins to pray for a miracle. His prayers soon lead him to ponder his purpose in life as he searches for a response to the feeling in his heart that there is some role for him in Jamie's illness, something for him to do. Landon soon discovers that purpose and asks Jamie to marry him, even in her weakened state. She agrees, and just as in her vision of her wedding day, hundreds of guests turn out for her wedding. Jamie's slow, painful walk down the aisle is, indeed, "a walk to remember."
In the last chapter of the novel, 57-year-old Landon reflects on the 40 years that have passed since his wedding to Jamie. He still loves her and has not removed his wedding ring in all those years. When he reveals that he now believes in miracles, readers are left to ponder the ending: Did Jamie die, or did a miracle save her life?