Leptobrachella fritinniens is a common Slender Litter Frog of lowland rainforests in Sabah. It has recently been delimited from L. dringi and L. gracilis. It is distinguished from the latter most importantly by its bipartite vocal sac and call characteristics. It seem to tolerate secondary forests and mild human alterations of the habitat. The original description was by Dehling and Matsui (2013) and the type locality is Camp 5 (114 m a.s.l.) at Gunung Mulu National park

L. fritinniens is medium sized frog. Males reach ~34 mm, females 48 mm in snout-vent length. It can be distinguished from other members of the subgenus Leptolalax in Leptobrachella by: 

It is relatively large in size, with males measuring 32–34 mm in snout-vent length (SVL) and females 46–48 mm. The snout is rounded, both when viewed from above and the side. The distance between the eyes (interorbital distance) is smaller than the width of the upper eyelid. The male vocal sacs are located under the throat (subgular) and are bipartite (split into two spaces). The toe webbing is only basal, meaning it covers only the base of the toes. The skin on the back and the dorsal side of the head is shagreened (roughened) with tiny tubercles. The supratympanic fold (a fold of skin above the eardrum) is angled. The pectoral glands are small. The species lacks supraaxillary glands and ventrolateral glandular ridges. The belly (venter) is spotted. Its advertisement call consists of a long series of 8 to 289 notes, of which each is made up of three or four pulses. The dominant frequency is very high pitched and ranges from 7225 to 9190 Hz and shows prominent frequency modulation.

The coloration of the dorsum is often dark gray with several light brown flecks and large, irregularly shaped black spots. The area below the canthus rostralis (the ridge between the eye and snout) and the ventral edge of the supratympanic fold are black. The coloration lightens to light gray on the lateral surfaces of the trunk and becomes almost white on the venter (belly). The dorsal surfaces of the limbs are light gray, marked with dark gray, black-edged crossbars. The area around the tibio-tarsal joint (ankle) is cream-colored. There are several cream-colored stripes along the edges of the jaws, and similarly colored crossbars on the upper arms and on the dorsal surfaces of the fingers and toes. A prominent light gray stripe runs from between the nostrils to the front edge of the upper jaw. The venter is patterned with large light gray spots. The throat, the front part of the breast, and the ventral side of the forelimbs are moderately densely speckled. The ventral surfaces of the thighs, tibia, tarsus, and the postaxial sides of the forelimbs are heavily speckled with dark brown. The posterolateral part of the throat, where the vocal sacs are located, is largely unpigmented. The iris is dark gray in the lower two-thirds and reddish gray in the upper third, with a ruby-red inner edge around the pupil.