Jill is a young student at Experiment House who is magically transported to Narnia alongside her classmate Eustace. Quick-tempered but eager to prove herself, she is tasked by Aslan with an important quest to find Narnia's lost prince. She must memorize and follow four specific signs to ensure their success, though her tendency to become overwhelmed sometimes clouds her judgment.

Eustace is a student at Experiment House who has previously visited Narnia and experienced significant personal growth during his travels. He relies on his past experiences to travel safely through the magical land and tries to act as a steadying presence for Jill. His loyalty to his old Narnian friends drives his determination to complete their dangerous mission.

Puddleglum is a Marsh-wiggle, a humanoid creature with long limbs and webbed hands, who resides in the marshlands. He possesses his species' trademark pessimism, constantly predicting dismal outcomes for their journey. Despite his gloomy exterior, he serves as the children's steadfast guide and maintains an unwavering faith in Aslan's instructions.

Aslan is the great, godlike lion who created and watches over Narnia. He acts as the ultimate moral and spiritual authority, bringing the children to his mountain to assign them their quest. Rather than solving problems directly, he provides guidance through signs, expecting his followers to trust his wisdom even when circumstances become difficult.

Prince Rilian is the son of King Caspian who vanished a decade before the children's arrival in Narnia. He originally set out to avenge his mother's death at the hands of a green serpent but disappeared after encountering a beautiful, mysterious woman. His absence has left Narnia without a clear successor to the aging king.

The Lady of the Green Kirtle is a beautiful and highly persuasive woman who crosses paths with the travelers in the northern wastelands. Traveling alongside a silent knight, she speaks sweetly to the children, offering them tempting advice about finding warm beds and food at a giant castle. Her charming demeanor conceals her true, darker intentions regarding Narnia's future.

King Caspian is the aging ruler of Narnia and an old friend of Eustace from decades prior in Narnian time. Now elderly and grieving the prolonged absence of his only son, he sets sail to seek Aslan's counsel one last time. His departure forces the children to undertake their quest in secret.

Master Glimfeather is a large, talking white owl who notices the children's arrival at Cair Paravel. Cautious about defying the Lord Regent's strict rules during the daylight, he organizes a secret nighttime gathering of owls to inform Jill and Eustace about the history of the lost prince.

Trumpkin is an elderly, deaf dwarf who serves as the Lord Regent of Narnia while King Caspian is away. He is strictly loyal to the King's commands, absolutely refusing to allow anyone else to risk their lives searching for the missing prince, which forces the children to sneak away.

The Warden is a pale, sad-looking Earthman who commands a large patrol of armed gnomes in the deep underground caverns. He operates in the dark, sunless world beneath Narnia, strictly enforcing the borders of his domain and questioning any overworld intruders who fall into his territory.

Golg is an Earthman, or gnome, living in the deep magical caverns far below Narnia's surface. He shares information about the subterranean realms and the true origins of his people, who hail from an even deeper, fiery land called Bism.