AbstractObjectivesTo characterize the paleodiet of individuals from Formative Period (1500 B.C.–A.D. 400) Atacama Desert sites of Ancachi and Quillagua as a means of understanding the dietary and cultural impacts of regional systems of exchange.Materials and methodsThirty‐one bone samples recovered from the cemetery of Ancachi (02QU175) and in/around the nearby town of Quillagua were the subject of carbon and nitrogen stable isotope analysis of bone collagen and hydroxyapatite and multisource mixture modeling (FRUITS, food reconstruction using isotopic transferred signals) of paleodiet. These individuals were compared with nearly 200 other Formative Period individuals from throughout the region to identify differences in dietary behaviors.Results80.6% (25/31) of the samples yielded sufficient well‐preserved collagen and were included in the multisource mixture model. The FRUITS model, which compared individuals with a robust database of available foods from the region, identified a wide diversity of diets in the Ancachi/Quillagua area (including both coastal and interior individuals), and, most notably, thirteen individuals who consumed an average of 11.2 ± 1.9% terrestrial animals, 19.8 ± 1.9% legumes, and 22.5 ± 3.1% marine fauna, a balanced pattern of protein consumption distinct from both the coastal and inland individuals in our larger regional sample.ConclusionsThe combination of stable isotope analysis and multisource mixture modeling permitted the characterization of dietary behavior of 25 individuals from nodal sites in the Atacama Desert, thus enhancing our understanding of the economic and social relationships that bound together Formative Period sites, populations, and individuals in this hyperarid region.