The feral pig is an exotic species in the Sierra La Laguna Biosphere Reserve, Baja California Sur, Mexico, and is considered harmful to the woodlands and tropical deciduous forest because of its foraging habits. To determine the taxonomic, nutrient, and energy content of the feral pig diet in this area, stomach contents of forty feral pigs were analyzed during the dry and rainy seasons in the woodlands and the tropical deciduous forest. Results indicate that feral pigs are frugivore-herbivore and stenophagous, feeding on a high percentage of fruits and seeds (77–87%) that provide high metabolizable energy (8293–11,585 kJ kg^–1 dry matter) and moderate crude protein (94.1–151.6 g kg^–1 dry matter) year round in the woodland and during the dry season in the tropical deciduous forest, or high percentage of leaves, stems, and tubers (44%) that provide low metabolizable energy (4740 kJ kg^–1 dry matter) and moderate crude protein (107.5 g kg^–1 dry matter) in the rainy season in the tropical deciduous forest. Therefore, diets based on fruits and seeds favor a lower quantity of food to meet the energy for maintenance of feral pigs than those based on other plant tissues: pine nuts < acorns ≈ wild figs < leaves, stems, and tubers. The observed diet based on acorns, along with estimates of acorn production results in a carrying capacity estimate of 0.031 adult feral pig ha^–1 yr^–1 during years of low acorn production. Thus, feral pigs in the area use fruits and seeds in both woodlands and tropical deciduous forest because of their quality as food resources. The availability of the food resources preferred by pigs (pine nuts, acorns, fan-palm fruits, and wild figs) during the year can be used to inform potentially sustainable feral pig carrying capacities and establish hunting programs.