Microhyla perparva is a very small forest floor species. The maximum snout-vent length is 15 mm in females but most specimens and male in particular are smaller in the range of 10–13 mm. (Smaller than the similar M. petrigena).

The frogs are colored in shades of brown above with dark markings on the shoulder and a light band on the flank. There are only 3 fingers on the hand. Toe tips are expanded. 

This tiny species is abundant locally, but rarely found in the leaf litter. However, after heavy rains hundreds of males emerge and congregate in water filled depressions. Breeding groups are active during the day (possibly at night too) and males float inflated and call at the surface of the pool in small territories trying to clasp any female that comes into reach and fight off other males.

Tadpoles of this species are very delicate and mostly transparent. Viewed from above they are dark grey. The tail bears a brown cross band in the distal third (faintly visible on the photo below). The tail terminates in a flagellum.

Tadpoles are mid water column suspension feeders. The lack keratinized mouthparts. The mouth is terminal. The spiraculum is located in a medial position on the venter. Undisturbed, tadpoles move very slowly with beats of the tail flagellum. 

The eyes of the tadpole are far lateral on the head.