The Lion, the Witch and the Wardrobe

Lucy's siblings, Peter, Susan and Edmund, do not believe her about Narnia at first, but later they all find their way to Narnia.

Lucy is the first of the Pevensies to enter Narnia through a magical wardrobe in the Professor's old house, into Narnia in the One Hundred Year Winter, under the rule of the White Witch, the evil self-proclaimed Queen of Narnia. There she meets Mr. Tumnus the Faun and, then later, the Beavers. However, her brother Edmund had also slipped into Narnia on the second occasion Lucy had entered, and encountered the White Witch while she was visiting Mr. Tumnus. Edmund, who had already jeered at Lucy about her "magical" country, continued to be spiteful towards Lucy by denying that either of them had been in Narnia. When the children all enter Narnia, Edmund slips away from the house of the Beavers and defects to the White Witch.

While travelling with Peter, Susan and Mr. and Mrs. Beaver to the Stone Table, they meet Father Christmas, who gives them gifts. Lucy is given a vial with magical cordial that can heal almost any injury, and a small dagger with which to defend herself "a great need". Edmund, meanwhile, had tried to betray the Beavers and joined the White Witch; he had first met her and been seduced by promises of power after first entering the wardrobe when trying to follow Lucy on her second entry to Narnia.

She and her companions arrive at Aslan's camp, and later that night, she and Susan comfort Aslan as he walks to his death – although they do not know of his fate at the time. Both girls also witness his sacrifice. While their brothers are going to war, Lucy and her sister see Aslan come back to life and help him wake the creatures in the White Witch's castle, which the White Witch had turned to stone. They meet with their brothers at the end of the battle.

At Cair Paravel, she is crowned as Her Majesty Queen Lucy by Aslan to the throne as co-ruler of Narnia, this marking the fulfilling of the ancient prophecy and the end of the White Witch's reign. During her reign, she is named Queen Lucy the Valiant. She and her siblings make a Golden Age in Narnia.

Years later, while hunting the White Stag through Lantern Waste, she and her siblings notice the lantern where she met Mr. Tumnus. The Pevensies return through the wardrobe into England, where no time has passed and they are children again.

Prince Caspian

Lucy travels to Narnia again with her three siblings. Lucy is the only one to see Aslan at first, and she has a terrible time convincing her brothers and sister as well as Trumpkin the dwarf that he had returned, echoing her trials early in the first book. However, Edmund believes her and backs her up. Aslan tells her to try again and says that she must follow him alone if they refuse to come with her. Lucy comments that Aslan has grown larger, but really she is the one who has grown.

The Voyage of the Dawn Treader

While Susan travels with Mr. and Mrs. Pevensie to America and Peter studies with Professor Digory Kirke, Lucy, Edmund and their cousin Eustace are drawn into Narnia through a magical painting in The Voyage of the Dawn Treader. This is very much Lucy's book, written largely from her point of view. However, in the end, Aslan firmly tells her and Edmund that they have become, like Susan and Peter, too old to further experience the wonders of Narnia.

The Horse and His Boy

The events in The Horse and His Boy take place after the siblings are crowned, and before they return to England, in The Lion, the Witch and the Wardrobe, and Queen Lucy is a young woman who rides to the aid of Archenland. She is described by Prince Corin as being more like a tomboy, unlike her sister, Queen Susan, who is a "proper lady". She helps King Lune to welcome Aravis to Anvard and helps to get Aravis's room and clothes ready.

The Last Battle

In The Last Battle, she plays a minor part as she returns to Narnia again with her brothers, High King Peter and King Edmund, along with Eustace Scrubb, Jill Pole, Polly Plummer, and Digory Kirke. There, she witnesses the destruction of Narnia and lives in the new Narnia created by Aslan. In the new Narnia, all the people and animals who lived in the previous Narnia during its existence return and join together. Lucy also meets her old friend Mr. Tumnus the Faun again, and Aslan tells her about a railway accident that occurs in England in which she, her brothers, her parents, Polly, Digory, Eustace and Jill die. She and Digory, Polly, Peter, Edmund, Eustace and Jill stay in Aslan's homeland for eternity, however, Susan remains living on Earth, her final fate undetermined.