The film was originally to release on November 25 but was pushed back to December 4 to coincide with the Krampusnacht, a traditional Austrian festival held on December 5 that celebrates the Krampus coming to punish naughty children.
They made a point of having the film's first act be strictly a "Christmas movie" before having it turn towards horror and dark fantasy.
Michael Dougherty describes the Krampus in this film as Santa Claus's shadow: "He's not the unstoppable monster that kicks down your door and rampages and grabs you. There's something darkly playful about him. He's having a good time doing what he does, and he enjoys the cat-and-mouse aspect of it."
The Krampus's final design was distilled from various postcards and illustrations of the creature over the years.
The visible breath in the cold exteriors was done digitally, but a major component of it involved filming real people in freezers reading dialogue for the scenes. Their breath was then isolated and added optically into the shots.