The Danish-American actor starred as Mahershala Ali's driver in the film, which took home the Best Picture, Best Original Screenplay, and Best Supporting Actor prizes at the 2019 Oscars.
However, while the film received critical acclaim, it was also criticised by many - including the living relatives of Black pianist Don Shirley, played by Ali in the movie - for portraying a stereotypical "white savior" narrative, a cinematic trope which often appears in American cinema, wherein a white protagonist is portrayed as a messianic figure who often learns something about him or herself in the course of rescuing non-white characters from their plight.
Mortensen opened up about the backlash in an interview with Britain's The Independent newspaper, as he said, "Much of the criticism that was levelled at that movie was not only unreasonable, but it was inaccurate, mendacious, and irresponsible. It's based on a load of bulls**t and an axe to grind and little else. Does it affect what I'm doing, or how people perceive me as an actor? Maybe it does. But I can't really do anything about that."
He also takes issue with the "cliche" description of criticism of the film, adding, "It's become a cliche to say, 'Is this movie going to be the Green Book of this year?' Green Book has become a pejorative."