The Earth Island Institute was founded in 1982 by environmentalist David Brower. It organizes and encourages activism around environmental issues and provides public education. Funding comes from individual members and supporting organizations. Through fiscal sponsorship, it provides the administrative and organizational framework for many individual projects that would otherwise be duplicating administrative requirements.

Some of the projects have enjoyed significant success: a consumer-led boycott resulted in 100% of American tuna becoming dolphin safe. The Earth Island Institute also provides dolphin safe certification for canned tuna producers.

The Mangrove Action Project was originally part of the Earth Island Institute, but became a separate organization in March 2007.

Earth Island has presented the Brower Youth Awards, named for founder David Brower, to six young environmental leaders since 2000.

Earth Island Journal has been published by the institute for 20 years. It includes environmental reporting and commentary from around the world.