Mouglalis was born in Fréjus,[3]Var, to a French mother and a Greek father. She spent her youth in the Vardépartement, before moving back to Nantes with her family. Her father is a doctor and her mother is a physical therapist.
Along with her career as an actress, Mouglalis began a successful modelling career. In 2002 she was chosen by Karl Lagerfeld for the ad campaign for the Amateur Allure de Chanel perfume. He used her as one of his "muses,"[4] promoting Chanel bags, fine jewelry, and watches.[2]
On 7 March 2007, she gave birth to her first child, a daughter named Saul, whom she had with French director Samuel Benchetrit.[4]
In February 2024, she joined actresses Judith Godrèche and Isild Le Besco in accusing Jacques Doillon of sexual misconduct, claiming that he forcefully kissed her in the summer of 2011 when Benchetrit was appearing in Doillon's film Un enfant de toi.[7]