Females have a snout-vent length of, while the corresponding measurement for males is. The tip of the snout extends just over the lower jaw and is pointed bluntly. The arms are slender and the fingers are long and black with brown-gold spots. The lips are swollen. The pupil of the eye is horizontally elliptical. P. diesmosi is mainly dark brown and has irregular darker markings and/or minuscule white patches. Specimens are sometimes almost totally black and brown with golden highlights. Golden patches can be found on the head, and its limbs are mainly golden-brown. The throatcolourranges from cream to dark brown, and the chest and stomach are also variably coloured, from dark brown with white patches to cream.