Annie Leonard was born in 1964 in Seattle, Washington, where she also grew up. She graduated from the Lakeside School, and has an undergraduate degree from Barnard College and a graduate degree from Cornell University in city and regional planning. She has a daughter named Dewi, born in 1999. As of November 2009, she lived in the Bay Area with her daughter.

Leonard is best known as the creator and narrator of the animated documentary about the life-cycle of material goods, The Story of Stuff. The documentary began as an hour-long talk, and was made into a condensed film version based on popular demand. She also published a book version of the film, released on March 9, 2010 by Free Press of Simon & Schuster. The UK edition of the book was published by Constable & Robinson on May 27, 2010. The German edition was published on March 12 by Econ Verlag.

After The Story of Stuff, she has created The Story of Cap and Trade on the topic of emissions trading as well as, in 2010, The Story of Bottled Water and The Story of Cosmetics.

In addition to her work on the Story of Stuff documentary, Leonard is also co-creator and coordinator of GAIA ( Global Alliance for Incinerator Alternatives) and serves on the boards of International Forum for Globalization and the Environmental Health Fund. She previously held positions with Health Care Without Harm, Essential Information and Greenpeace International, and was coordinator of the Funders Workgroup for Sustainable Production and Consumption. In 1992 she testified in front of the US Congress on the topic of international waste trafficking.

Leonard has been criticised for misrepresentation of sources and misleading usage of scientific terms, by Lee Doren of the Competitive Enterprise Institute. Doren has responded to several of Leonard's videos by way of Fair Use critiques that superimpose Doren's comments and graphics to Leonard's original videos. CNN and Fox News have subsequently reported on his criticism.