Although Tapanti was a national wildlife reserve for many years, it was converted into a national park in 1992. It has an area of 6,080 hectares and ranges from 1,220 meters above sea level to 2,560 meters. It is located in the upper reaches of the Orosi Valley and contains the headwaters of the Rio Grande de Orosi.

The park is mostly lower montane and premontain rainforest. The annual rainfall is usually more than 6,500 mm and has passed 8,000 mm. The Rio Grande de Orosi (and its tributaries) is the source of considerable hydroelectric energy and supplies much of San Jose's drinking water.

The flora and fauna of the region are extraordinary. In part this is due to the heavy rainfall and in part because the park is part of a whole complex of ajoining parks running all the way down into Panama. The Americas' largest moth, Thysania agripina is common here.