Born in New York City, he was educated at the United States Naval Academy in Annapolis, Maryland. In 1879, backed by James Gordon Bennett, Jr, owner of the New York Herald newspaper, and under the auspices of the US navy, Lieutenant DeLong sailed from San Francisco, California on the ship "Jeannette" with a plan to find a quick way to the North Pole via the Bering Strait.
The ship became trapped in the ice and eventually was crushed and sank. DeLong and his crew abandoned ship and set out for Siberia in three small boats. After reaching open water, they became separated and one boat was lost, no trace of it was ever found. De Long's own boat reached land, but only two men sent ahead for aid survived. The third boat, under the command of Chief Engineer George W. Melville, reached the Lena delta and was rescued.
George Washington DeLong died of starvation near Mat Vay, Yakutsk, Siberia. Melville returned a year later and found the body of DeLong and his boat crew. Overall, the doomed voyage took the lives of nineteen men.
A diary that DeLong kept was edited by his widow and published in 1884 under the title, The Voyage of the Jeannette.