Polypedates leucomystax is a treefrog that closely follows human activities. It is commonly found around villages, artificial forest edges, and along roads, where it breeds in ditches and puddles. The type locality is Java, however. the species is widely distributed in the Sunda region. The vertical distribution ranges from sea level to at least 750 m a.s.l. This species does not enter deep into primary forests. 

The adult size up to 50 mm snout-vent length in males, while females can measure up to 70 mm SVL. The body appears slightly more stocky than in other Polypedates. The head is triangular, a canthus rostralis is present, and the snout is long and ends in a relatively blunt tip. Limbs are long and all digits are equipped with adhesive disks. A thin, almost straight supratympanic fold is present. The eardrum is visible. The pupil is elliptical and horizontal. 

The coloration ranges from light to mid-brown, with four dorsal longitudinal stripes visible in most individuals and distinct leg banding; some populations are without such stripes. The underside is white. It resembles Polypedates macrotis but can be distinguished by subtle differences in coloration and proportions. The head is slightly broader in P. macrotis and the eyes are more forward directed than in P. leucomystax. 

Reproduction occurs via eggs laid in foam nests, usually laid on the surface of water bodies and attached to vegetation or twigs. Tadpoles are grey-green to brown on the dorsal side. A light spot on the snout is a common feature. The eyes are positioned far lateral. A horizontal pigment stripe is located at the tail base, bordered above by a pigment-free stripe. The ventral side is silvery-white, including the spiracle and cheeks, which almost reach the eye. Tadpoles grow to a total length of 40–50 mm. Their tail fin is narrowly pointed, resembling a flagellum. We have consistently found these tadpoles in stagnant water, primarily in puddles—often ephemeral—with silty bottoms and at least partial sunlight exposure.