The most prominent theme of A Thief of Time by Tony Hillerman is multiculturalism. This theme is represented by Joe Leaphorn and Jim Chee, two members of the Navajo tribe and officers with the Navajo Tribal Police. Joe and Jim often find their duties conflicting with their culture, and they struggle to maintain their identity in a white-dominant society.

Another theme presented throughout the book is justice. Joe in particular struggles with this concept, as the law does not often lead to true justice. This theme is most prominent when Brigham Houk, a schizophrenic fugitive wanted for murdering his family, kills Randall Elliot, a greedy archeologist who committed two murders out of greed. Despite Brigham's crimes, it is accepted that his illness is responsible. Elliot, on the other hand, represents true evil.

This sets up a perfect backdrop for the exploration of the major theme of the novel—cross-cultural relationships. Leaphorn and Chee are members of a racial minority. They are Navajo policemen who try and balance their traditional cultural values with the reality of living in a predominantly white culture. Chee is very rigid in his attempts to live his life in the traditional Navajo fashion, while Leaphorn bends a little easier to the dominant white culture.

Hillerman depicts the Navajo culture as one that is harmonious with nature and more concerned with family relationships than with material wealth. He contrasts this with his depiction of white culture, which is shown as materialistic, competitive, and lacking the depth of Navajo culture. A Thief of Time is a great exploration of the many issues that arise when one is trying to keep a traditional way of life alive in a mainstream culture that opposes it.