We describe a new species of Cnemaspis from southern Sumatra, Indonesia. The new species is the first Cnemaspis reported from Sumatra and is a large (52.6–58.7 mm in snout–vent length [SVL]) nocturnal species. A combination of the following characters distinguishes the new species from all other Southeast Asian congeners: adults reaching 58.7 mm SVL; supralabials 13 or 14; infralabials 11 or 12; tricarinate ventrals; precloacal pores absent; moderately prominent, randomly arranged, dorsal tubercles; 20 or 21 paravertebral tubercles; no tubercles on lower flanks; caudal tubercles encircling tail; subcaudals keeled; the median row of subcaudals not enlarged; two postcloacal tubercles on each side of tail base; no enlarged femoral, subtibial, or submetatarsal scales; subtibial scales keeled; 28–34 subdigital lamellae on fourth toe; dark and light caudal bands distinct in both sexes. We tentatively assign the new species to the Cnemaspis kendallii group of the Southern Sunda clade of recent phylogenetic analyses.