The nonnative snail Radix auricularia was found at 4 previously unknown locations in Wyoming. At Two Ocean Lake in Grand Teton National Park, R. auricularia was found with trematode infections that were the same cercarial type found in native snails during the same sampling period. Although finding parasitic infections in a nonnative species challenges the enemy release hypothesis, the presence of trematodes in R. auricularia may act to suppress population growth of this snail, thereby emolliating the negative impact this snail may have on native populations. Further research assessing the prevalence of trematode parasites in R. auricularia would aid in understanding whether this nonnative snail harbors parasites across its invasive range, which could have ramifications for parasitism of local waterfowl and wildlife in these habitats.