A new Tetradactylus from Udzungwa Mountains is described on the basis of one adult male and one adult female. The species has tridactyle forelimbs with the longest toes bearing four scales, didactyle hind limbs, 14 dorsal longitudinal row scales, four femoral pores and frontoparietals in broad contact. This combination of morphological characters distinguishes the species from the similar T. eastwoodae, a South African endemic. The new species has smooth head scales, six ventral rows, and the male possess on either side of the vent a prominent claw-like scale lacking in the female. The species has been found in swampy montane grasslands at about 1880 m. It is syntopic with three other specialised grass lizards: Ellenberger's long-tailed Seps (Tetradactylus ellenbergeri), Zambian grass lizard (Cordylus macrolepis), and the Grass-top skink (Mabuya megalura).