The guajón has a light to dark brown coloration on the dorsal area. Males have a yellow coloration on the ventral area that can extend from the vocal sac to the abdomen and flanks, while females are uniformly white on the ventral area.

The guajón coquí is the second largest Eleutherodactylus frog species in Puerto Rico, with females being larger than males. The guajón coquí is characterized by large bulging dark eyes and large truncate disks at the end of its long feet.

Measurements
Length: Approximately 1.7 to 2 in (4.3 to 5 cm)

The guajón's voice is low and melodious, consisting on a series of three to seven notes of the same type and almost sounds like an echo. Only males will actively call during the late afternoon and night. To a lesser degree, they also call during daylight hours. 

Eleutherodactylus frogs are known as direct developers, because they do not go through the usual tadpole stage. Guajón females lay eggs on the rocks surface. Embryonic development occurs inside the eggs that later hatch into miniature copies of the adults.

The actual life span of the guajón is unknown. The common coquí frog, Eleutherodactylus coqui, can to live for two years in the wild, but is known to live longer in captivity. 

The reproductive activity of the guajón increases in the rainy and hotter months of the summer and fall, and decreases in the cooler and drier winter months. The female coquí guajón typically lays an egg mass on the rock surfaces with an average of approximately 16 eggs. The male guajón provides parental care to the egg mass by keeping the eggs hydrated and protecting them from predators. One male guajón can provide care to multiple egg masses from different females. In approximately 20 to 29 days eggs hatch into tiny frogs, of 0.34 inch (8.7 millimeters) in length on average. This is the most critical life stage for these animals.

The guajón is native to Puerto Rico and is restricted to the southeastern part of the island. The name guajón is derived from the unique rock formations of the species habitat known as guajonales. These are caves and cavities made of plutonic, granitic or sedimentary rocks. Structurally the caves are complex, in the form of several chambers of irregular shape and size, and at different depths between the surface of the ground and stream. These unique ecosystems are associated to streams and natural drainage areas.

The species also lives within forested rocky stream banks covered with moss, ferns and other vegetation. The combinations of streams, rocks, boulders and surrounding forest provide a wide variety of retreat sites for the species that help in the conservation of humidity. It is within these rocks, boulders, crevices and grottoes where the species hides during the day and use to lay eggs. The guajón has also been found in artificial structures like culverts. 

The guajón coquí is an important primary consumer of invertebrates. They can eat a large variety of insects like cockroaches and crickets, as well as other invertebrates like spiders.