A new species of the Scinax catharinae group is described from Misiones, northeastern Argentina. It is characterized by the dark yellow flash colors in hidden areas of thigh and shank; robust but not hypetrophied forearm; and lack of a thick glandular patch in the inguinal region. It is closely related to Scinax berthae, from which it can be distinguished by having a more robust forearm and less toe webbing. In addition, relative to S. berthae, males of the new species are slightly larger and the few known females are notably larger.