La Amistad International Park sustains over 115 species of fish, 250 species of reptiles and amphibians, 215 species of mammals, and 600 species of birds. Among these exists an incredible ensemble of threatened, endangered, and endemic species. Based on these characteristics, La Amistad received World Heritage status because it fulfills every criterion for natural sites, as determined by the Operational Guidelines of the World Heritage Convention.

One hundred species of mammals has been recorded, such as the howler monkey, black-handed spider monkey, white-throated capuchin monkey, and the night monkey or jujaná (Aotus lemurinus). The park protects important populations of threatened species like Baird’s tapir, groove-toothed squirrel, olingo (Bassaricyon gabbil) and the shrew.

The five species of cats found on the Isthmus are also present in this area.

There are 91 amphibious species recorded in the park, including the harlequin frog and the spiny toad. Among the 61 species of reptiles one may find the spectacular mountain salamander, the striking and lethal coral snake and the oropel snake.