Hypophthalmichthys molitrix (Silver Carp) is an invasive fish that threatens ecosystem function by consuming basal food web resources. In this study we quantify gut contents of 83 Silver Carp in the mainstem reservoir ecosystem of Kentucky Lake, Kentucky, Tennessee River Valley, United States. Silver Carp guts contained phytoplankton (63.5%), zooplankton (33.8%) and heterotrophic flagellates (2.7%) based on volume. Additionally, we compare existing literature on Silver Carp diet and trophic position (i.e., stable isotope information). Our study indicates that Silver Carp are planktivorous and consume organisms within multiple lower trophic levels across a range of habitats. However, we show that Silver Carp diets differ at finer taxonomic scales and suggest these differences may be driven by forage availability. To our knowledge, this is the first study to quantify diets of Silver Carp within a mainstem reservoir ecosystem designed for flood storage with a comparison to existing Silver Carp diet literature. The results of this study may be useful in predicting ecological implications of Silver Carp invasion across a diversity of habitats.