I studied the diet of the Golden Eagle (Aquila chrysaetos) in western Iran by identifying food items in prey remains, pellets, and video recordings at seven nests during the 2011–2013 breeding seasons. Two methods were used to calculate diet composition: minimum number of individuals of each prey species and estimated biomass for prey items. I identified 316 prey items, which included five species of birds, four species of mammals, and two species of reptiles. Mammals made up the greatest proportion of the diet, 44.0% by frequency and 76.8% by biomass, and birds accounted for 43.7% of the diet by frequency and 17.7% by biomass. Cape hare (Lepus capensis), Chukar (Alectoris chukar), Common Magpie (Pica pica), large-toothed souslik (Spermophilus fulvus) and common fox (Vulpes vulpes) were the most important prey species. The percentage of mammals in the Golden Eagle’s diet in western Iran was lower than in North America, Scotland, the mountains of the Mediterranean, and across Europe and Asia.