Invasive species are of concern to natural resource managers and conservation biologists. The New Zealand mudsnail (Potamopyrgus antipodarum) has invaded many freshwaters of the western United States with unknown consequences on the native benthic invertebrate fauna. We conducted a laboratory investigation to determine if mudsnails affected the growth of the desert valvata snail (Valvata utahensis), a species native to the Snake River in southern Idaho. Results indicated that increasing densities of mudsnails limited the growth rate and absolute growth of the desert valvata. We suggest that absolute growth is a better metric than growth rate for comparing snail species and assessing interactions between them.