Dennis Stock was born in 1928 in New York City. At the age of 17, he left home to join the United States Navy. In 1947 he became an apprentice to Life magazine photographer Gjon Mili and won first prize in Life's Young Photographers contest. He joined Magnum in 1951.

Stock managed to evoke the spirit of America through his memorable and iconic portraits of Hollywood stars, most notably James Dean. From 1957 to 1960 Stock made lively portraits of jazz musicians, including Louis Armstrong, Billie Holiday, Sidney Bechet, Gene Krupa and Duke Ellington for his book Jazz Street. In 1968 Stock took a leave of absence from Magnum to create Visual Objectives, a film production company, and he shot several documentaries. In the late 1960s he captured the attempts of California hippies to reshape society according to ideals of love and caring. Then throughout the 1970s and 1980s he worked on color books, emphasizing the beauty of nature through details and landscape. In the 1990s he went back to his urban origins, exploring the modern architecture of large cities. His recent work was mostly focused on the abstraction of flowers.

Stock generated a book or an exhibition almost every year since the 1950s. He taught numerous workshops and exhibited his work widely in France, Germany, Italy, the United States and Japan. He worked as a writer, director and producer for television and film, and his photographs have been acquired by most major museum collections. He served as president of Magnum's film and new media division in 1969 and 1970.

Dennis Stock resided in Woodstock, New York, and his widow is the author Susan Richards.