Beart was born Emmanuelle Béhart-Hasson in St. Tropez, on the French Riviera, the daughter of Geneviève Galéa, a homemaker and former model, and Guy Béart, a singer and poet. Beart's mother is of Greek, Maltese, and Italian descent, and her father is of Spanish, Swiss, and Russian ancestry. After a ten-year relationship with Daniel Auteuil (her co-star in Manon of the Spring, A French Woman and A Heart in Winter), she divorced him and re-married.

In addition to her screen work, Béart is also known for her social activism. She is an ambassador for UNICEF, and has made news for her opposition to France's anti-immigration legislation. In 1996, she made headlines when, defending the rights of the "sans-papiers" (illegal immigrants). She was forcibly removed after her group’s occupation of a Paris church.