Joshua Hammer was born in New York and educated at Horace Mann and Princeton University, graduating with a BA in English literature. In 1988 he joined Newsweek Magazine as a business and media writer, transitioning to the magazine's foreign correspondent corps in 1992. Hammer served, successively, as bureau chief in Nairobi, Buenos Aires, Los Angeles, Berlin, Jerusalem, and Cape Town, and also was the magazine's Correspondent at Large in 2005 and 2006. He was a Nieman Fellow at Harvard University in the 2004-2005 academic year.
Since leaving Newsweek in 2006, Hammer has been a contributing editor at Smithsonian Magazine and Outside. He also writes frequently for the New York Review of Books, and has contributed often to GQ, The New York Times Magazine, and countless other US publications. He was a finalist for the National Magazine Award in reporting in 2003, and won the award, for his writing about the Ebola crisis in West Africa, in 2016. He is also the author of five non-fiction books, including The New York Times bestseller, The Bad-Ass Librarians of Timbuktu, which was published by Simon & Schuster in April 2016, and The Falcon Thief, published by Simon and Shuster in February 2020. Hammer lives with his partner and their eight-year-old son.