The Bull Run is home to more than 250 species of fish and wildlife. The lower Bull Run River is home to four fish species that have been listed as threatened under the Endangered Species Act and include fall and spring Chinook salmon, winter-run steelhead, and coho salmon.

The major species of wildlife in the Bull Run include deer, elk, cougar, black bear, and rodents. This heavily forested ecosystem does not provide much food for these species, so the number of animals per acre in the Bull Run is estimated to be quite low.