A young woman named Amélie lives a modest life as a waitress in Paris, her existence colored by her vivid imagination and a desire to bring joy to those around her. She was raised by eccentric parents who mistakenly diagnosed her with a heart condition, leading her to spend most of her childhood in isolation, without attending school or socializing with other children. As a result, she develops a rich fantasy life and a unique perspective on the world around her. Her life takes an unexpected turn when she discovers a small tin box containing childhood treasures hidden away in her apartment by a boy decades ago. This discovery instills in her a purpose; she decides to return the box to its now-grown owner if she can find him. Enthralled by the joy her action brings, she becomes resolved to bring happiness to others in little, inventive ways.

Amélie's quest to spread cheer takes her on a series of whimsical escapades around her quaint neighborhood of Montmartre. In the process, she encounters a cast of quirky characters, each with their own dreams and struggles. These include her reclusive neighbor who paints the same Renoir painting yearly, a grocer with a mean streak, a hypochondriac coworker, and a man who collects discarded photo booth pictures. Amidst her good deeds, Amélie wrestles with her own isolation and yearns for connection. A chance encounter with a quirky young man fixated on a mysterious photo album sets her on a personal journey that challenges her to overcome her shyness and fear of taking risks in her life.