Delaware Canal State Park has two designated state park natural areas - Nockamixon Cliffs and River Islands. These areas contain threatened or endangered species and are unique natural environments. Visitors are welcomed to explore these areas, but are asked to abide by the old saying, "take only pictures, leave only footprints." Camping within a natural area, including the river islands, is prohibited.

Topography, geology, and scenic beauty combine to create the unique character of the Nockamixon Cliffs Natural Area. These sheer cliffs tower 300 feet above the Delaware River and dominate the landscape. Because the cliffs face the north, they receive little direct sunlight. This cool habitat supports an alpine-arctic plant community unusual this far south.

Their substrate deposited by glacial waters nearly 10,000 years ago, eleven state park river islands are now protected natural areas within a river corridor that is experiencing dramatic economic growth. The islands provide critical habitat for migratory waterfowl and songbirds, and contain sites of archaeological importance.

The Delaware River is the longest free-flowing river east of the Mississippi River and serves as a major migration corridor for birds and for the American shad. The park maintains six public recreation areas with shoreline access to the river. Of the many islands in the river, eleven are protected as the Delaware River Islands State Park Natural Area.

At Easton, the park is making environmental restoration history at the Fish Passageway. This structure is allowing the passage of the American shad, a migratory fish, from the Delaware River to its historic spawning areas in the Lehigh River. Passage had been blocked for over a century by a dam. A viewing window within the passageway lets visitors witness the passage of many fish species through the ladder. Each spring, the Delaware River Shad Fisherman's Association sponsors an annual Shad Tournament in Easton.