It is famous for its large population of wild Japanese Macaques, also known as the Snow Monkeys. They go to the valley during the winter, foraging elsewhere in the national park during the warmer months. Starting in 1963, the monkeys descend from the steep cliffs and forest to sit in the warm waters of the hotsprings, and return to the forests in the evenings.

The park is located in the monkey's natural habitat, in the forests of the Jigokudani valley in Yamanouchi.

The park is open all year round, but it is especially interesting to see the monkeys when the area is covered in snow, from December to March. Monkeys enter the bath around the year, but they sometimes need some encouragement to do so by park wardens throwing food into the pool, especially during the warmer seasons of the year.