The type locality of Philautus mjobergi is Gunung Murud, at 2133 m a.s.l (7000 ft.). Philautus mjobergi belongs to a confusingly variable species group and inhabits submontane to montane forests (900–3000 m a.s.l.). Philautus mjobergi closely resembles P. nephophilus in overall size, possessing long hind limbs, a relatively broad head, half-webbed toes, and a moderately tubercular dorsal skin texture. Both species, however, are highly variable in their color patterns. They can be distinguished by the shape of the snout, which is acuminate in P. nephophilus and more broadly rounded in P. mjobergi, in both males and females. Consult Dehling et al. (2016) for side-by-side comparisons. The specimen photograph presented here originates from Gunung Murud.

Philautus mjobergi is a small, stocky frog. Males reach 18–24 mm in snout–vent length; females 22–32 mm. The snout is rounded when viewed from above and below and is shorter than the eye diameter. All digits end in expanded adhesive discs. Finger webbing is rudimentary, whereas the toes are less than half-webbed. The heels bear a small tubercle. The dorsal skin is often relatively rough (though some individuals are remarkably smooth), with scattered enlarged tubercles, particularly on the head, eyelids, and shoulders. The supratympanic fold is well developed and curved. The eardrum is indistinct.

Egg deposition has been reported in Nepenthes pitchers. Given the taxonomic uncertainties within the species group to which P. mjobergi belongs, these older reports should be verified by future research. The lifestyle of this species at distances from any stream, however, give plausibility to those reports. Direkt development is a possible mode of development.