She began playing small roles in films in 1949, with impressive performances in the Fernandel vehicle Meurtres? (Three Sinners, 1950) and alongside Jean Gabin as a showgirl/gangster's moll in the film Touchez pas au grisbi (1954).
She achieved prominence as the star of Elevator to the Gallows (1958), directed by Louis Malle, and Jules et Jim (1962), directed by François Truffaut.
Most prolific during the 1960s, Moreau continued to appear in films into her 80s.