Reports of limb malformations in amphibians have increased in the last 20 y. In California, this includes anuran species in the families Hylidae and Ranidae. While working with Foothill Yellow-legged Frogs in Sonoma County, we observed a malformation of a hind limb in 1 individual, the source of which was undetermined. We believe this to be only the second such report of a malformation in this declining species.