The Up in the Air star won the role thanks to her likeness to McVie and her musical talents - the actress is a trained pianist.
She'll join Aaron Eckhart, who will portray Wilson, in The Drummer.
The film charts the last six years of Wilson's life. He and McVie had a passionate and tumultuous relationship in which they served as each other's inspiration.
Farmiga will both sing and play the piano in the film.
Director Randall Miller tells WENN, "She has a number of duets with Eckhart in the film. The combination of Aaron and Vera will be pure magic."
The film starts shooting in June (12).