We describe a new species of Thoropa, previously identified as T. lutzi, from the northern region of the Serra da Mantiqueira in the Atlantic Forest domain in Southeast Brazil. The new species is diagnosed by the following combination of characters: small size; slender body; head longer than wide; dark colored nuptial pads on the inner side of the Finger I and on the internal carpal tubercle; nuptial pads with epidermic cone-shaped papillae measuring of 53.1–91.6 μm in diameter, and at a density of 14–32 papillary epidermic projections/mm2; presence of vocal sac and vocal slits; and advertisement call with 5–10 harmonics, duration of 0.23–0.42 s, and peak of frequency of 2060–4470 Hz. With the description of the new species, T. lutzi is now only known for the state of Rio de Janeiro.