Wild pigs (Sus scrofa) are considered opportunistic omnivores that consume primarily plant matter; vertebrates are thought to constitute only a minor component of their diets, primarily as carrion, but active predation on vertebrates has been suspected. We examined the stomach contents of 104 wild pigs collected during a 7-year period in oak woodlands of the Diablo Range, California, and found that 40.4% contained vertebrate prey comprising 20 species, including 11 mammals, and totaling 167 individuals. Most stomachs with vertebrate prey included multiple individuals (≤18) of >1 species (≤6). Predation occurred in both male and female pigs and was most frequent during summer and fall, probably in response to protein deficiency in the diet. Wild pigs are a conservation concern because of their rooting behavior and consumption of mast; our results extend their potential impact to include predation on vertebrates, especially small mammals.