The micro-endemic Philautus amoenus has been known only from Gunung Kinabalu where it inhabits high-elevation mossy forests, at 1800–2500 m a.s.l.

This frog ranges from 24 mm (males) to 35 mm (females). The body shape is relatively stocky with rounded to pointed snout. The legs are only moderately long. Toes and fingers bear terminal adhesive disks. Toes webbed to about one third, fingers without webbing. The dorsal skin bears tubercles and some ridges. 

As in most Philautus coloration in P. amoenus may vary greatly. Most specimens are brown above with dark markings. But reddish, blackish or greenish colorations have also been documented. Smith (1931) described the holotype as "Very dark brown above with whitish (yellow in life) spots or markings more or less connected to each other and forming a definite pattern, namely an oval patch on the nape, an elongated one down the middle of the back and a band along either flank; a white bar between the eyes and white spots on the lips; limbs banded with dark and white. Below whitish, heavily powdered with brown." 

This frog has not been observed very often and little is known about its habits. According to Malkmus et al.(2002), male calling activity peaks between 18:00 and 20:00 h. Males call from vegetation below 150 cm; Inger et al. (2017) reported calling males from up to 3 m in vegetation. The latter authors described the call as a short seris of usually three (2–4) rapidly repeated, rasping notes, the last of which is about three times as long as the other notes.