Diets of two zooplanktivores were studied in Lake Winnipeg: the non-indigenous rainbow smelt (Osmerus mordax) and the native cisco (Coregonus artedi). Gut contents of smelt (70-130 mm total length) and cisco (100-200 mm TL) were concurrently collected with zooplankton (integrated vertical tows) from pre-determined locations throughout Lake Winnipeg in 2010 and 2011. When spatially separated, both zooplanktivores showed similar shifts from preference for fast-moving copepods during low total zooplankton density to slow-moving large cladocerans (Daphnia spp. and Eubosmina sp.) during high total zooplankton density. When spatially overlapped in the North Basin, dietary overlap was high between smelt and cisco, but possible vertical segregation was apparent during daylight-dark trawls. Diel variation in smelt diet was minimal. Overall, impact of smelt on the food web seemed weaker than in other smelt-invaded lakes, potentially owing to the warm, shallow nature of Lake Winnipeg providing a poorer quality habitat than cooler, deeper lakes.