We investigated diet and its relationship to trophic morphology in Sternotherus odoratus (Stinkpot) in northwestern Pennsylvania on Presque Isle, Lake Erie. Three taxa were most prevalent in fecal samples: invasive Eurasian mussels, small snails, and trichopteran larvae. No sexual difference in diet was apparent, although males had relatively wider heads than females. Significant positive correlation of proportion of sample volume composed of mussels with width of the head and alveolar surfaces was accompanied by nonsignificant negative correlation of proportion composed of snails with both variables. The results thus suggest a shift in molluscan prey preference with increasing size of the trophic apparatus. Total consumption of mollusks was high relative to most other reports of Stinkpot diet. In the Laurentian Great Lakes, the Stinkpot is the second turtle species found to prey heavily upon invasive mussels and thereby participate in transferring production from the pelagic zone to the littoral zone.