Ella (Eloise Webb) lives with her wealthy parents in a beautiful estate in a peaceful kingdom. From a young age, she is taught by her mother (Hayley Atwell) to believe in the existence and presence of magic, allowing her to befriend the many animals on the estate, particularly the mice. Everything is perfect until her mother contracts a fatal illness. On her deathbed, she makes Ella promise that she'll always have courage and show kindness to others.

Years later, Ella's (Lily James) father (Ben Chaplin) reveals that an old acquaintance, Lord Tremaine, has passed away and that he has chosen Tremaine's widow (Cate Blanchett), who has two daughters of her own, Drizella (Sophie McShera) and Anastasia (Holliday Grainger), as his second wife. Ella welcomes her step family warmly, despite the stepsisters' less than pleasant attitudes and her needing to protect her friends from her stepmother's cat, Lucifer.

Soon after, Ella's father goes abroad on business. Sadly, he becomes ill and also dies. This new loss results in Lady Tremaine revealing her true cold, wicked nature. Desperate for money, she dismisses the servants and forces Ella to do all the work. Even worse, she gives Ella's room to the stepsisters, forces her to sleep in the attic, and won't even let her eat with the family. One morning, after Ella, not wanting to sleep in the cold attic, sleeps by the fireplace, her soot covered face leads her stepsisters to dub her Cinderella, which Lady Tremaine (and even Ella herself) calls her.

Crushed by their cruelty, Ella goes for a ride in the woods, where she encounters a hunting party. She meets one of the hunters (Richard Madden), who claims to be an apprentice named Kit who lives in the palace. Unknown to her, he's actually the only son of the land's dying king (Derek Jacobi). Despite never learning her name, Kit (a nickname given to him by his father) is enchanted by Ella's charm, kindness, and unique outlook on life and becomes obsessed with her. Upon learning that he has little time left, the King insists that Kit find a bride at an upcoming ball. Despite the law saying that he must marry a princess, Kit can't get over the mystery girl and talks his father into letting every eligible maiden in the land attend.

When the ball is announced, the Tremaine family is ecstatic at the prospect of marrying into royalty. However, when Lady Tremaine refuses to buy Ella a new dress, she fashions one herself from an old dress of her mother's with help from the mice. The night of the ball, Ella tries to join her step family on the way out, but Lady Tremaine, claiming that her mere presence will disgrace them, leads her daughters in ripping up the dress before leaving without her.

Ella runs into the garden in tears and encounters an old beggar woman, who reveals herself to be her Fairy Godmother (Helena Bonham Carter). She uses her magic to turn a pumpkin into a magnificent carriage, four mice into horses, two lizards into footmen and a goose into a coachman, as well as turning Ella's dress into a gorgeous blue gown complete with glass shoes before sending her on her way with the warning that the spell only lasts until midnight.

At the ball, Ella wins the coveted first dance with Kit, whose true identity she's pleasantly surprised to learn. This irritates the Grand Duke (Stellan Skarsgård), who's secretly promised Kit to a princess, a fact Lady Tremaine overhears. After dancing, Ella and Kit tour the palace and grounds together, slowly falling in love, but before he can learn her name, the clock strikes 11:59, forcing her to flee, dropping one of her glass shoes in the process. She manages to get away before the stroke of midnight and hides the other shoe in her room as a memento.

Soon after, the King dies, but not before giving his son permission to find his love. Once it's announced that every maiden in the kingdom is to try on the shoe, Ella goes to her room for hers, only to find Lady Tremaine waiting with it in hand, having figured out her identity from her attitude after the ball.

Lady Tremaine demands that Ella make her head of the royal family and give her daughters proper husbands when she becomes queen and when she refuses, Lady Tremaine smashes the shoe and locks Ella in her room. She then brings the shoe and identity of the mystery girl to the Grand Duke and talks him into rewarding her with title of countess and worthy husbands for her daughters. He takes the shattered shoe to Kit, hoping to convince him to forget the mystery girl, but this makes him more determined than ever to find his love.

The Grand Duke and the captain of the guards (Nonso Anozie) lead a garrison to try the remaining shoe on all the maidens in the land, all of whom are rejected by its magic, before arriving at the Tremaine estate. When the shoe rejects both stepsisters, they turn to leave, only to hear Ella singing thanks to the mice opening her bedroom window.

The Grand Duke tries to leave anyway but is stopped by one of the men, who reveals himself to be Kit in disguise and demands that the captain investigate the sound. Once Ella is found, Lady Tremaine tries to forbid her from trying on the shoe, but is overruled by the captain. Sure enough, the shoe fits and Ella leaves with Kit after forgiving her stepmother, who later is forced to leave the kingdom with her daughters and the Grand Duke, never to return.

Kit and Ella are married and crowned king and queen. The Fairy Godmother narrates that they become the land's most beloved monarchs, ruling with the courage and kindness she promised her mother.