We determined the seasonal diet of the Andean fox Lycalopex culpaeus in three habitats in the Atacama Desert, northern Chile, by analyzing their scat contents. We estimated the biomass and the number of individuals of each prey species consumed and compared our results with those of other studies on Lycalopex foxes in Chile and South America. In general, the L. culpaeus diet was characterized by a generalist behavior and higher dietary breadth than those in other ecosystems. In contrast with the other biomes of southern Chile and South America, insects represented the most frequent prey species in the present study and the main food item, comprising more than 50% of all prey at the three study sites; however, in terms of biomass, rodent and reptile prey showed the highest percentage from summer to winter. Significant differences were found between the biomass consumed among sites. Likewise, we found a relationship between the niche breadth of the diet and the primary productivity of the sites. Statistically significant differences in prey items consumed were noted across seasons and sites located at different altitudes, which reflected an opportunistic response to the availability of prey. Our report contributes to current data about the natural history of L. culpaeus in hyper-arid habitats.