According to director Steve McQueen, Colin Farrell (Jack Mulligan) and Robert Duvall (Tom Mulligan) improvised many of their scenes.
After a three-decade career playing more than 75 mostly supporting roles, this film marks Viola Davis's first lead role in a major studio movie.
First feature film directed by Steve McQueen that does not have Michael Fassbender in the cast. Fassbender had starred in McQueen's three previous movies: Hunger (2008), Shame (2011), and 12 Years a Slave (2013). Prior to this, McQueen had only directed short films.
After being cast in the movie, Michelle Rodriguez began working with an acting coach, this being the first time she had received acting lessons since her motion picture debut in the Sundance darling Girlfight (2000) eighteen years prior. The acting coach worked with her on one of the tougher emotional scenes, in which her character confronts and then kisses a man who is also mourning the loss of a spouse.
Composer Hans Zimmer worked briefly on the original Widows (1983) television series on which this film is based, as an assistant to the show's composer Stanley Myers.