When her mother dies, her father drops little Gabrielle Chanel (Lisa Cohen) and her sister off at an orphanage run by nuns. She grows up feeling abandoned, which has a deep impact on her character. Years later, Gabrielle (Audrey Tautou) and her sister Adrienne (Marie Gillain) earn a living as seamstresses and cabaret singers. Gabrielle catches the attention of Etienne (Benoit Poelvoorde), a wealthy womanizer and racehorse owner who gets her audition at a fancy nightclub. After failing in the audition, she decides to go see her sister in the countryside. On the way, Gabrielle stops for a surprise visit with Etienne whose chateau is vast beyond her wildest fantasies. Assuming the nickname he has given her, "Coco," she decides to capitalize on a good thing and stay with him for as long as she can.

Etienne revels in sex with her and wants her to be his little geisha. She suffers from deep mood swings. She is clearly talented as a seamstress, but she's stuck in a rut. Slowly, she takes in the ostentatious women's fashions of the times and comes up with an alternative look, which she tries on Emilienne (Emmanuelle Devos), Etienne's former mistress who is an actress. A simple straw hat is a big hit, and Coco shows up at a dance with an elegant dress she has created.

Coco's sugar daddy doesn't know what to make of her inventiveness so she turns to Arthur "Boy" Capel (Alessandro Nivola), an Englishmen who works for Etienne. He is attracted to her and appreciative of her newfound creativity. They spend a magical two days at the sea together. Boy has other surprises in store for Coco that will have a lasting impact upon her life.

Co-screenplay writer and director Anne Fontaine has fashioned a bittersweet portrait of the early life of the legendary fashion icon who popularized black dresses, hats without frills, and simple but elegant clothes. She draws out a solid performance from Audrey Tautou who vividly conveys Coco's quest for love and her determination to find her own way in life. Benoit Poelvoorde is excellent as Etienne, who progresses from a playboy, to a spoiled and selfish tyrant, to an older man who wants to wed the woman who has captured his heart. Coco Before Chanel shows the difficulties women have in forging their own path in a man's world.