Frogs in the genus Cycloramphus are endemic to the Brazilian Atlantic Forest domain and many are threatened or endangered. Cycloramphus species lay eggs either on moist rocks or in moist soil cavities on the ground. Tadpoles of only 8 of the 28 recognized Cycloramphus species are known. Herein we describe the tadpole of C. rhyakonastes on the basis of specimens collected at the type locality in southern Brazil. Cycloramphus rhyakonastes is an aquatic breeder with semiterrestrial tadpoles that live on moist rocks within the splash zone of high gradient streams. We compare the C. rhyakonastes tadpole with all congeneric tadpoles described to date and discuss adaptations in this specialized tadpole and those of other species that adhere to rocky substrates.