Intense predation on larval and juvenile fishes by introduced piscivores can be detrimental to recruitment of threatened and endangered native fishes. Introduced largemouth bass (Micropterus salmoides) in the San Juan River, New Mexico, Colorado, and Utah, rarely are collected as adults; however, juveniles (<200 mm total length) often occur in the same habitats as young-of-the-year native fishes. To evaluate the prevalence of native fishes in the diet of juvenile largemouth bass, stomach samples from juveniles were collected from the San Juan River in New Mexico during July and August 2005, when young-of-the-year native and nonnative fishes were present. Stomach contents of largemouth bass were identified as native catostomids, native cyprinids, or nonnative cyprinids based on pharyngeal teeth. Although nonnative fishes comprised >80% of the potential prey base, significantly more native fishes were identified in stomachs than nonnative fishes. The disproportional abundance of native fishes in the diet of juvenile largemouth bass suggests greater susceptibility of young-of-the-year natives to predation by largemouth bass in the San Juan River.