Umbra pygmaea (Eastern Mudminnow) is a freshwater species common in Atlantic slope coastal lowlands from southern New York to northern Florida and is typical of slow-moving, mud-bottomed, and highly vegetated streams, swamps, and small ponds. We examined its seasonal food habits at the Great Swamp National Wildlife Refuge (NWR), NJ and at the Croatan National Forest, NC. A total of 147 Eastern Mudminnow from 35–112 mm TL and 190 Eastern Mudminnow from 22–89 mm TL were examined from these sites, respectively. At both locations, we found it to be a bottom-feeding generalist that consumes cladocerans, ostracods, chironomid larvae, coleopteran larvae, and other insects and crustaceans. Ostracods were most common in the diet at the Great Swamp NWR and occurred in 62% ± 2.5% of the stomachs with food. At Croatan National Forest, chironomid larvae were most common and occurred in 66.7% ± 15.8% of the stomachs. There were no statistically significant differences in diet composition between the sites during the winter, summer, and fall. However, when compared on an annual basis, Jaccard’s Index (θJ = 0.636, P = 0.05) suggested that the diet at the two study sites was significantly different. While we identified the same major food groups at both locations, the utilization of these food groups varied seasonally. Detritus was a major stomach content at both locations throughout the year. We also documented cannibalism during the summer season at both locations. The seasonal diet of the Eastern Mudminnow was similar to that of Umbra limi (Central Mudminnow) and Umbra krameri (European Mudminnow). Our findings here are the first quantitative examinations of seasonal differences in the diet of the Eastern Mudminnow within its native North American range.