The study of dogs recovered from archaeological sites in the Southern Cone of South America has seen exponential growth in recent years, encompassing a wide range of thematic areas. Despite the growing interest in archaeological dogs, paleodietary reconstructions remain scarce. This study addresses that gap by analyzing the diets of dogs recovered from burial contexts at the El Olivar Diaguita site (ca. 1190-1536 AD) to evaluate the socioecological dynamics between these animals and humans. We employed two complementary lines of evidence: stable isotope analysis (delta C-13 and delta N-15) and the study of plant microremains preserved in dental calculus. For the stable isotope analysis, we present measurements of local fauna (n = 28). The results from the Bayesian mixing models (MixSIAR) suggest that these dogs had diverse diets (marine- and camelid-focused), derived from a broad-spectrum feeding behavior that included direct provisioning by humans, access to latrines, predation on small animals, and, to a lesser extent, scavenging of communal middens. The discovery of starch grains (Zea mays, and Nicotiana spp.) showing signs of anthropogenic processing strengthens the evidence of human control over Canis familiaris diet. Notably, the presence of the psychoactive plant Nicotiana spp. in the dental calculus of a violently sacrificed pathological dog raises new questions about the ceremonial/medicinal use of psychoactive substances by canids in the Andes.