Matthiessen bases the majority of his writing on his personal travels. He writes about vanishing cultures, oppressed people, and exotic wildlife and landscapes, combing scientific observation with lyrical, intellectual prose that connects the world of art and the world of the natural sciences. Novelist William Styron described Matthiessen's books as "the work of a man in ecstatic contemplation of our beautiful and inexplicable planet. . .we behold a writer of phenomenal scope and versatility."

The author of 24 books, Matthiessen's novels include Killing Mr. Watson (1990), the first work of a proposed trilogy; Race Rock (1954); Partisans (1955); Radizer (1961); At Play in the Fields of the Lord (1965), which was nominated for a National Book Award and was adapted into a film; and Far Tortuga (1975), widely considered to be his most accomplished work. His fiction also includes a collection of short stories, On the River Styx (1989).

Matthiessen is equally well-known for his nonfiction writing based on his travels to the far reaches of the world. The Snow Leopard (1978), which recounts his trip to the remotest parts of Nepal, won a National Book Award. His other nonfiction works include Wildlife in America (1959), Under the Mountain Wall (1962), In the Spirit of Crazy Horse (1983), Men's Lives: The Surfmen and Baymen of the South Fork (1986), Baikal: Sacred Sea of Siberia (1992), and East of Lo Monthang: In the Land of Mustang (1995).

Matthiessen founded the Paris Review, along with Harold L. Humes, and was its first fiction editor. He has received numerous awards for his work including the Gold Medal for Distinction in Natural History (1985), the John Burrough's Medal 1982), the African Wildlife Leadership Foundation Award (1982), and election to the American Academy of Arts and Letters in 1974.