In the spring and summer of 2020, we found cysts of the nematode Eustrongylides spp. in Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss), and Mountain Whitefish (Prosopium williamsoni) in the Deschutes River. The prevalence and maximum intensity of infection exceeded the range of published accounts for Eustrongylides spp. across a wide range of species. Because the 1st intermediate host is likely to be a tubificid worm, also known as a sludge worm or sewage worm, this exceptional prevalence of Eustrongylides spp. infection raises questions about conditions in the river that may be contributing to the high infection rate in fish.