Radula yamadae, a species from mountain ranges in the Atlantic forest, is described here as new to science. The new species is characterized by plants occasionally epiphyllous, densely branched, leaf lobes imbricate, ovate, apex obtuse to subacute, cell walls thin, trigones small, lobules distant to contiguous, rarely imbricate, subquadrate, 1/2-2/5 the lobe length, base rounded to obtuse, covering 1/3 to overlapping the stem, keel conspicuously convex, strongly inflated at rhizoid area and along the keel, and rhizoids numerous. A complete description and illustration of the new taxon as well as comments on morphology, taxonomy, and distribution are provided.