Found on the western side of the Nicoya Peninsula, this refuge has 162 hectares of land areas and 587 hectares in the sea.

The very large Ostional Beach, together with Nancite Beach in the Santa Rosa National Park, is the most important nesting site for the olive ridley (Lepidochelys olivacea) on Earth. The refuge includes a large mangrove swamp at the mouth of the Nosara River. Over 100 birds have been identified in the area.