The food habits of naiads of Isoperla nana Walsh (Plecoptera: Perlodidae) have not been well studied. Based on findings in other species of Isoperla, we hypothesized that the trophic level of I. nana varies across developmental instars and seasons. Gut content analyses of the naiads as well as carbon (C) and nitrogen (N) stable isotope analyses (SIA) of I. nana, other macroinvertebrates, biofilms and plants collected from Jordan Creek (Vermilion County, Illinois) were examined to assess the feeding habits of I. nana. Gut content analyses showed that I. nana naiads ingest animals (probably including chironomids and oligochaetes), diatoms, amorphous detritus, algae and plant material. Based on the food assimilated, SIA confirmed that they are omnivores. A shift in food utilization between sampling periods in spring was observed, but ontogenetic change of feeding habits could not be disentangled from seasonal shift due to the small number of individuals available for analyses. This study provides new insights into the feeding ecology of I. nana.