The 43-year-old actress is well known for her BAFTA winning role as Elizabeth Bennet in the successful 1995 miniseries 'Pride and Prejudice'.
Ehle will play Carla, who is the mother of Anastasia Steele, the college student who falls for 27-year-old billionaire Christian Grey. Dakota Johnson is starring as Steele and Charlie Hunnam will play Grey, the Hollywood Reporter said.
Universal and Focus Features' forthcoming adaptation, based on EL James' racy and extremely popular novel, is being directed by Sam Taylor-Johnson and produced by Michael De Luca and Dana Brunetti alongside author James.
She was also tapped for a role in upcoming heist movie "The Forger".