A wide variety of natural conditions have combined to provide a high diversity of habitats within Big South Fork. The Big South Fork River contains over 60 species of fish, including channel catfish, sunfish, muskellunge, and smallmouth bass. In addition, walleye, striped bass, and white bass do migrate upstream from Lake Cumberland.
The varied terrains of Big South Fork offer an equally high diversity of habitats for mammals and birds. Large native mammals found in the area include white-tailed deer, black bear, which were released experimentally in the mid-1990s, and elk, which have migrated into the area from state-managed lands. Small mammals ranging from raccoon to bobcat and gray fox are present throughout the park.
Over 160 species of birds, migratory and resident, have been recorded in Big South Fork in recent years. Improving habitat should lead to increasing numbers of birds being recorded in the park.