Beart obtained an acting role in the 1976 film Tomorrow's Children. In her teens she appeared in bit parts in television then went to Montreal, Canada to work as a nanny before returning to France the following year to attend drama school in Paris. A short time later she was cast in her first adult role in a film, and in 1986 she achieved fame with her role opposite Yves Montand, in the film Manon des Sources. For her performance, she won the 1987 César Award for "Best Supporting Actress". She also won a "Best Actress" award at the Moscow International Film Festival for her starring role in the 1995 film, A French Woman.

In addition to her award for Best Supporting Actress, she has also been nominated for 6 César Awards for Best Actress in the following performances:

In 2003, Béart, aged 40, appeared nude on the front cover of French magazine Elle and as of 2007, it is still the magazine's biggest-selling issue ever.