The Scinax catharinae clade comprises the S. perpusillus and S. catharinae groups. The S. catharinae group has 38 species, mostly from Brazil's Atlantic Forest. We describe a new species of S. catharinae group based on external morphology, color pattern, and bioacoustics. The new species calls from herbaceous vegetation of slow-flowing streams from Santa Teresa, State of Espírito Santo, southeastern Brazil. The new species is distinguished from species of the S. catharinae group by the following combination of characters: male SVL 24.8–28.3 mm and female SVL 31.2–38.6 mm; males with hypertrophied forearms and inguinal glands; interocular region with a dark blotch not exceeding beyond the anterior margin of tympanic level; black blotches on a whitish-green background on the inguinal region and hidden surfaces of legs; call type A of 0.301–0.883 s, and 12–30 notes emitted at a rate of 31.4–42.0 notes/s. We also provide remarks on its natural history and conservation status.