This film concentrates on two hours in the life of a French singer waiting on the results of a cancer test.

One afternoon in Paris, Cléo, a beautiful chanteuse, awaits the results of tests to determine whether or not she has cancer. In the interval, she visits a fortune-teller and is horrified when the tarot cards confirm her fears. She seeks consolation with Angèle, her companion and manager, in a cafe. They visit a shop where Cléo views herself in a mirror, obtaining reassurance that she is still young and beautiful, and buys a hat. Returning to her Montparnasse home, Cléo is visited by her lover, a busy man who can offer her only a moment of polite concern. Her songwriter and pianist arrive to rehearse a new number, but the song suddenly recalls her fears and she leaves, unable to tolerate the banter of the musicians. At a cafe she plays one of her own recordings, but no one listens. She visits her friend Dorothée, an artist's model, and together they deliver some film to Dorothée's lover, a motion picture projectionist. He projects a short comedy film for them, and Cléo momentarily forgets her anxiety. Dorothée breaks her mirror as they leave, and again Cléo becomes upset and wanders about the city. As 7 o'clock approaches, she strolls through the Parc Montsouris and meets Antoine, a young and good-natured soldier enjoying his last few hours of leave before returning to Algeria. She tells him of her situation, and he promises to accompany her to the doctor's office. Cléo is now able to face the verdict with courage.