Limnonectes gunungensis is, like other Guardian Frogs belonging to the palavanensis-species group, is a relatively small species among dicroglossids but a relatively large species among the Guardian Frogs:  males measure upt to 32 mm and females up to approximately. 39 mm in snout-vent length.

The distributional range of the species includes the mountain ranges of eastern Sarawak (Murud, Mulu, Dulit, Pa' Lungan). Reported records came from elevations between 1000–1600 m, i.e., in transitional areas between submontane rainforest and lower montane rainforest. The species was found sympatric with Limnonectes sarawakensis on Gunung Dulit and with L. nephophilus around Camp 3 on Gunung Mulu. 

According to the original publication, the Mountain Guardian Frog shares several features with other Guardian Frogs of the palavanensis-species group: a finely shagreened dorsum, marked by prominent longitudinal dorsolateral glandular ridges. The interorbital distance is equal to or greater than the width of the upper eyelid. Its toes are not fully webbed, and a distinctive horseshoe-shaped dermal ridge is present in the middle of the back, just behind the point where the arms are inserted. 

This species, however, is distinguished from all other members of the palavanensis-species group by the combination of several features, including extensive toe webbing, a subangular supratympanic fold, and a clearly visible pineal spot located at the level of the anterior edge of the upper eyelid. The vomerine ridges are long and narrowly separated from each other. A moderately distinct postpalpebral ridge runs along the front part of the dorsolateral ridge, extending only just beyond the level of the arms. It lacks both lumbar and median ridges.

Little is know about the species' natural history. This Guardina Frog species populates the moist leaf litter in primary rainforest. As other Guardian Frogs do, they deposit their eggs in the leaf litter. The clutch is guarded by the male. Once tadpoles hatch, tadpoles climb on the back of the male which transports them to a nearby body of stagnant water. The tadpoles are similar in size, body contour, color pattern and tail fin shape to other Guardian Frog species; distinguishing characters have not been worked out yet. 

The advertisement call is hitherto unrecorded.