The Topeka shiner Notropis topeka is an endangered fish species, historically described as inhabiting cool, headwater prairie streams. However, Topeka shiners recently have been found in off-channel habitats with high temperatures and low concentrations of dissolved oxygen. In laboratory experiments to determine whether Topeka shiners can tolerate the conditions in these off-channel habitats for extended periods, we found that their optimum temperature for growth was approximately 27°C and their critical thermal maximum was 39°C at a 31°C acclimation temperature. Topeka shiners grew at dissolved oxygen concentrations as low as 2 mg/L, but at a considerably lower rate than at 4 mg/L and above. The concentration of dissolved oxygen that was lethal for 50% of the fish after 96 h at 26°C was 1.26 mg/L. Growth was reduced by Asian tapeworm infections. Overall, high temperatures and low dissolved oxygen are probably not limiting factors for Topeka shiner populations in most off-channel habitats.