Great Horned Owls (Bubo virginianus) have a wide distribution in Mexico, and other countries in America, where they are important predators. Therefore, our objective was to study the diet of this species in "El Gallo", Municipality of Vanegas, in the Sierra La Mojonera, in San Luis Potosi, Mexico, to analyze the diversity of its diet and the percentage of biomass contributed by each prey species. We collected and analyzed 57 pellets and various skeletal remains of mammals, birds, reptiles and arthropods, some of which were in the pellets and others were found in the perching sites of B. virginianus in a small rock cave. Most of the prey remains were complete skulls, bone parts or fragments of small mammals (79.2 %), arthropods (15.5 %), birds (3.5 %) and reptiles (1.7 %). The most frequently consumed species were rodents such as Dipodomys ordii (11.3 %), Chaetodipus nelsoni (10.6 %) and Sigmodon hispidus (7.7 %). The Shannon-Wiener (H' = 2.50) and Simpson (D = 0.914) diversity indices showed that B. virginianus has a diverse diet and a broad trophic niche. The Pielou index showed high evenness (J'=0.86), indicating that B. virginianus has no preference for any of its prey. The diet content of B. virginianus depends on the diversity and availability of prey in its habitat. In the present study, D. ordii and C. nelsoni were the most abundant prey species and those that provided the greatest biomass to B. virginianus in this region. We also found remains of hares and gray foxes next to the pellets, but it was not possible to determine whether they came from hunted prey or were consumed as carrion. The presence of several skulls of the shrew (Notiosorex crawfordi) represents an additional record of this species in San Luis Potosi, which is considered an endangered species.