We describe a new species of narrow-mouthed frog of the genus Kaloula from the volcanic mountains of southern Luzon Island (Mt. Banahao, Mt. Isarog, and Mt. Mayon) and adjacent Polillo Island, Philippines. On the volcanoes of southern Luzon, the new species is found in habitats ranging from small dry stream beds to stationary pools of rivers in mid- to upper montane primary forest. On Polillo Island, the new species has been found near quiet streams in selectively logged primary forest and second growth near sea level. The new species presumably is allied to Kaloula rigida (a forest species endemic to northern Luzon Island) and to Kaloula picta (a more widespread Philippine endemic that is found in a variety of habitats) as indicated by possession of narrow disks on the digits and by the presence of supernumerary tubercles on the palmar surface of the manus. It differs from these species by its smaller body size, reduction of webbing on toes, absence or extreme reduction of outer metacarpal tubercles, and by characteristics of the advertisement call.