Born to Vasil Mili and Viktori Cekani in Korçë, Albania, Mili he spent his childhood in Romania, attending Gheorghe Lazăr National College in Bucharest, after which he came to the United States in 1923. In 1939, Mili landed a job as a freelance photographer for Life (a position he held until his death in 1984). Over the years his assignments took him to the Riviera (Picasso); to Prades, France (Pablo Casals in exile); to Israel (Adolf Eichmann in captivity); to Florence, Athens, Dublin, Berlin, Venice, Rome, and to Hollywood to photograph celebrities and artists, sports events, concerts, sculptures and architecture.
Working with Harold Eugene Edgerton of MIT, Gjon Mili was a pioneer in the use of stroboscopic instruments to capture a sequence of actions in one photograph. Trained as an engineer and self-taught in photography, Gjon Mili was one of the first to use electronic flash and stroboscopic light to create photographs that had more than scientific interest. Many of his notable images revealed the beautiful intricacy and graceful flow of movement too rapid or complex for the naked eye to discern. In the mid-1940s he was an assistant to the photographer Edward Weston.
Over the course of more than four decades, thousands of his pictures were published by Life as well as other publications. He died in Stamford, Connecticut on February 14, 1984, of pneumonia at the age of 79.