Mercier was born into a wealthy family; her father was a French pharmacist and her mother Italian.
Mercier initially wanted to be a dancer. The circumstances of war made this difficult and her parents saw it as only a whim; however, her determination won through and she joined the "ballet-rats", as the dancers of the chorus are termed. She soon advanced to soloist in the Nice Opéra. At the age of 15 she met Maurice Chevalier, who predicted that she would be a success.
She moved to Paris aged 17, and first joined the troupe of Roland Petit, then the company of the "Ballets of the Eiffel Tower". Parallel to her career as dancer, Mercier studied acting under Solange Sicard. For her film début her birth name seemed too long and old-fashioned. It was suggested she take the name Michèle: this happened to be name of her younger sister, who had died at the age of five from typhoid fever. However, she adopted the name as a tribute to the actress Michèle Morgan.
After some romantic comedies and a small role in
Tirez sur le pianiste
("Shoot The Pianist", 1960), she worked in England and made some films in Italy, mainly with a small budget and usually playing women of easy virtue.
Mercier needed a role which could make her a star. In 1963, when it was decided to make a movie of the sensational novel
. She almost signed a contract, but Mercier won the role after trying out for it: she did not appreciate this very much because she was being treated like a beginner at a time when she was already well known in Italy. At the time she was contacted to play Angélique, she had already acted in over twenty films. During the next four years she made five sequels which enjoyed great success. However the role of Angelique was both a blessing and a curse. It catapulted her to almost instant stardom, rivalling Brigitte Bardot in celebrity and popularity, but the character overshadowed all other aspects of her career. By the end of the 1960s, the names "Angélique" and Michèle Mercier were synonymous.
"When people talk with me they always refer to Angélique, but I have also played fifty other women. I have tried for a long time to forget about her. But now I see her as a little sister who is always by my side and I have learned to live with her."
