The Lost in Translation, The Island and Match Point star will be appearing in ad campaigns for the brand’s hair products.
She said: "It’s wonderful to be working with L’Oreal, a company that has celebrated independent women for years. I’m very excited to be part of this campaign, which is modern and fashion forward."
L’Oreal has had many celebrities as representatives, including Beyonce Knowles, Natalie Imbruglia, Eva Longoria and Claudia Schiffer.