The vegetation in the Acaraí State Park is predominantly dense lowland rainforest, with some dense submontane rainforest on two small, isolated elevations, and dense alluvial rainforest on some banks of the Acaraí River.
Fauna identified to date include 337 species of birds, 35 of reptiles (5 sea turtles, 1 freshwater turtle, 1 crocodilian, 6 lizards, 1 amphisbaenid and 19 snakes).