Ilha Grande is one of the most pristine remnants of Brazil's Atlantic rainforest, one of the richest ecosystems in the world, and a hotspot for biodiversity and conservation. It holds some of the largest remaining populations of many endangered species. The seas around the island, which are also protected, feature a unique convergence of tropical, subtropical, and temperate-zone marine life, and may be the only waters in the world where it is possible to see corals and tropical fish along with Magellanic penguins and Southern right whales.

The entire island is a protected area, with most of its territory included in Ilha Grande State Park and the island, which is roadless and off-limits to cars, features over 150 km of hiking trails connecting the handful of coastal villages and hamlets to one another and to the many beaches, mountain peaks, waterfalls, and pristine forests.