Seton was raised in North America, his family having emigrated to Canada in 1866. Drawn to nature, Seton resisted his family's attempt to make an artist of him. He gained experience as a naturalist by trailing and hunting in the prairie country of Manitoba in the final years of the 19th century. He used this knowledge as the basis for his animal stories. His artistic training enabled him to earn a living for a time as an illustrator of wild animals. He collected his stories into his most popular book, Wild Animals I Have Known (1898). He continued to write such books into the 1940s.

Deeply concerned with the future of the prairie, Seton fought vigorously to establish reservations for Indians and parks for animals threatened by extinction. In order to provide children with the opportunities for nature study, he founded the Woodcraft Indians in 1902 and later was chairman of the committee that established the Boy Scouts of America.