Gulf killifish, Fundulus grandis, have been introduced in the Lower Pecos River and are highly abundant in reaches of the Permian Basin region. Very little is known about the ecology of nonnative, inland populations of F. grandis. We investigated the feeding ecology of this species in the Pecos River using stomach contents analysis and laboratory feeding trials. Inland F. grandis were piscivorous, consuming more fish prey than has been reported from native coastal ecosystems. Predation by F. grandis could threaten native species in the Pecos River and other inland systems where it has been introduced.