Chanel has released some behind-the-scenes footage from the film, said The Hollywood Reporter.
Stewart, 25, as the popular fashion designer will be seen donning some covetable Victorian-inspired threads-complete with a frilly white collar-in the high-fashion period piece.
Lagerfeld, Chanel's creative director and the director of the movie, will premiere the film at the Chanel's Metiers d'Art show on December 1 in Rome.
The movie features Stewart and Geraldine Chaplin co-starring as actresses preparing to appear in a film as Chanel at different ages.
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This marks the fourth time Chaplin has embodied Chanel in the designer's films. She will play a middle-aged Coco Chanel.
As for Stewart, Lagerfeld said of his longtime muse, "She can look like Chanel, and I wanted to show Chanel through all the decades of her life and the comeback in the 1950s."
Jeremie Elkaim, Francois Marthouret, Amanda Harlech, Jamie Bochert, Jake Davies, Baptiste Giabiconi and Laura Brown will also star in the upcoming film.