The oriental weatherfish (Misgurnus anguillicaudatus) is invasive to 13 U.S. states and at least 9 other countries. Although this cryptic fish species is widespread, very little is known regarding its ecology. We used baited minnow traps to collect 237 individuals from water bodies connected to the Boise River, Idaho. To determine the diet of the fish within this invasive population, we dissected and examined stomach contents of the sampled fish. Most of the stomachs (158 of 237) were empty, and 42 contained only the trap bait. However, 37 contained natural food items. Gravimetric analysis, frequency of occurrence, and mean percent by number all indicated macroinvertebrates as the primary diet component, with chironomid larvae as the most numerous prey eaten. Graphical analysis of prey-specific abundance also indicated that oriental weatherfish fed on a generalized diet, of which detritus is likely an important part. An omnivorous diet may, in part, explain the species' ability to expand its invasive range quickly and successfully. Our findings add to a growing list of traits indicating that the oriental weatherfish fits the profile of a highly successful invader. As such, the oriental weatherfish should be a target species for further ecological research.