The natural habitat at McConnells Mill State Park is very diverse. Various stages of succession are found throughout the park and surrounding land from open fields to mature forest to the Slippery Rock Creek Gorge. The diverse habitats support a wide variety of wildlife species.

Chipmunk, squirrel, mink, raccoon, and other small mammals are found within the park. Larger mammals and game species, such as deer, black bear, and turkey, also can be spotted.

The creek corridor provides rearing and resting areas for migratory waterfowl. Raptor species, including osprey, bald eagle, and several species of hawk, use the creek as a food source.  The diverse habitat also attracts a variety of songbird species. 

The Slippery Rock Creek supports a variety of coldwater and warmwater fish species. Sections of the creek are stocked with trout by the Pennsylvania Fish and Boat Commission.  

A variety of reptiles and amphibians, including terrestrial salamanders, mudpuppies, frogs, lizards, and snakes, dwell near the creek and contributing streams.