Mood in No Country for Old Men is ominous, foreboding, tense, and suspenseful. This is to be expected given that characters hunt one another for much of the novel. McCarthy maintains this mood through the frequent use of foreshadowing and ominous imagery, as in the following passage from Chapter 1. In this passage, Moss returns to the desert to revisit the scene of the crime:
When the moon did rise it sat swollen and pale and ill formed among the hills to light up all the land about and he turned off the headlights of the truck.
The imagery of the moon in this scene sets the mood for the reader: the orb is "swollen," "pale," and "ill-formed," hardly signaling a pleasant evening. Returning to the scene of the crime can do Moss no good. Readers sense this from the imagery, anticipating trouble as the mood shifts.
Bell's monologues begin each chapter of No Country for Old Men, setting the mood effectively both for each chapter and for the novel as a whole. Foreshadowing features heavily as a device in these monologues, with Bell convinced that the outsized violence he experiences at work reflects broadly on the moral state of America.