We investigated the temperature tolerance and growth of 2 federally protected freshwater gastropods from southern Idaho: Valvata utahensis and Pyrgulopsis idahoensis. Snails were collected in the Snake River and transported to the laboratory where they were kept under highly controlled conditions. In varying-temperature, short-duration experiments, the temperatures tolerated by both species were between 7°C and 34°C. In constant-temperature, long-duration experiments, growth rates were between 0.004 mm · d⁻¹ and 0.016 mm · d⁻¹, and we created growth curves for both species that were previously lacking. Our results are among the first to report temperature tolerances and growth rates of native Snake River snails, and we discuss implications for the biology and management of both species.