With its variety of climatic conditions and surface features, Oregon has a diverse assortment of vegetation and wildlife, including 78 native tree species and 10 native mammals. The coastal region is covered by a rain forest of spruce, hemlock, and cedar rising above dense underbrush. Douglas fir is the state tree and an important source of timber. Where the Douglas fir has been destroyed by fire or logging, alder and various types of berries grow. In the high elevations of the Cascades, Douglas fir gives way to pines and true firs. The state's many species of smaller indigenous plants include Oregon grape—the state flower—as well as salmonberry, huckleberry, blackberry, and many other berries. Eighteen Oregon plant species were listed as threatened or endangered in 2003 which includes the Willamette daisy, Western lily, Malheur wire-lettuce, rough pop-cornflower, and MacFarlane's four-o'clock.

Out of the 130 species of mammals, 28 of them are found throughout the state.  Many species, such as the cougar and bear, are protected, either entirely or through hunting restrictions. The Columbian white-tailed deer, with an extremely limited habitat along the Columbia River, is still classified as endangered. Thirty-six Oregon animal species were classified as threatened or endangered in 2003 which includes the short-tailed albatross, bald eagle, Fender's blue butterfly, three species of chub, brown pelican, northern spotted owl, and three species of sea turtle. Deer and elk are popular game mammals. Among introduced mammals, the nutria and opossum are now present in large numbers. At least 60 species of fish are found in Oregon, including five different salmon species, of which the Chinook is the largest and the coho most common. The state also receives a lot of migratory birds which include large numbers of geese and ducks. Extensive bird refuges have been established in various parts of the state.