Kalophrynus heterochirus was described in 1900 by Boulenger. The type locality is simply recorded as "Borneo"; unfortunately, the exact location on the island where the type specimens originated is unknown. Inger (1966) assigned specimens from western Sarawak to this species. The individuals shown in the photos are from the Matang Range or Gunung Pueh, western Sarawak.

The body is relatively small, with males having a snout–vent length (SVL) of about 22–24 mm.

Kalophrynus heterochirus is a small frog species in the family Microhylidae. The dorsal skin is granular in texture. The dorsal coloration is commonly reddish-brown (sometimes referred to as purple-brown), although some specimens may be greyish above. At the groin, there are usually bluish-white spots embedded in a black blotch. A narrow white stripe extends from the eye—or anterior to the eye (canthus rostralis)—above the eardrum diagonally to the groin area. The underside is variably dusky on the throat and anterior chest, sometimes cream-colored on the posterior parts of the belly and underside of the thighs. Distinct subarticular tubercles are present on all fingers; the fourth finger is nub-like. The hind feet are about one-third webbed. The inner and outer metatarsal tubercles are only weakly developed.