The widow of credited screenwriter Donald E. Stewart found the "Hostiles" script when moving houses. Stewart, who died in 1999, had not shipped the manuscript to any studios, and his wife was surprised to come across it. After seeing Crazy Heart (2009) and Out of the Furnace (2013), she felt that Scott Cooper was the right man to shepherd it towards the screen.
The film was shot in chronological order.
Rosamund Pike revealed in an interview that she and Christian Bale barely spoke during filming outside of shooting their scenes, saying that Bale "would keep a distance. Our characters in 'Hostiles' are quite dysfunctional, but have this profound connection that we let happen without ever really talking about it."
The character of Yellow Hawk was written specifically for Wes Studi. Scott Cooper has said he wouldn't have made the film if Studi hadn't agreed to be in it.
The film went into production without a distributor. With a budget of almost $40 million, this was a huge gamble for financier Ken Kao.