Born in East Orange, New Jersey to Adelaide Sparkman and Joseph Russell Lynes. His younger brother was Joseph Russell Lynes, Jr. (1910–1991). Lynes spent his childhood in New Jersey but attended the Berkshire School in Massachusetts, where he was a classmate of Lincoln Kirstein (1907–1996). He was sent to Paris in 1925 with the idea of better preparing him for college. His life was forever changed by the circle of friends that he would meet there including Gertrude Stein, Glenway Wescott, Monroe Wheeler. He attended Yale University in 1926, but dropped out after a year to move to New York City.
He returned to the United States with the idea of a literary career and he even opened a bookstore in Englewood, New Jersey in 1927. He first became interested in photography not with the idea of a career, but to take photographs of his friends and display them in his bookstore.
Returning to France the next year in the company of Wescott and Wheeler, he traveled around Europe for the next several years, always with his camera at hand. He developed close friendships within a larger circle of artists including Jean Cocteau and Julien Levy, the art dealer and critic. Levy would exhibit his photographs in his gallery in New York City in 1932 and Lynes would open his studio there that same year.
He was soon receiving commissions from Harper's Bazaar, Town & Country, and Vogue including a cover with perhaps the first supermodel, Lisa Fonssagrives. In 1935, he was asked to document the principal dancers and productions of Kirstein's and George Balanchine's newly founded American Ballet company (now the New York City Ballet).
He was also most notably friends with Katherine Anne Porter, author of the novel Ship of Fools, with whom he often enjoyed photographing wearing elaborate evening gowns and occasionally reenacting Shakespeare.
During his lifetime, Lynes amassed a substantial body of work involving nude and homoerotic photography. In the 1930s, he began taking nudes of friends, performers and models, including a young Yul Brynner, although these remained private, unknown and unpublished for years] Over the following two decades, Lynes continued his work in this area passionately, albeit privately. "The depth and commitment he had in photographing the male nude, from the start of his career to the end, was astonishing. There was absolutely no commercial impulse involved — he couldn't exhibit it, he couldn't publish it." – Allen Ellenzweig, art and photography critic who wrote the introduction to George Platt Lynes: The Male Nudes, published in 2011 by Rizzoli.
In the late 1940s, Lynes became acquainted with Dr. Alfred Kinsey and his Institute in Bloomington, Indiana. Kinsey took an interest in Lynes work, as he was researching homosexuality in America at the time. A large number of Lynes' nude and homoerotic works were left to the Kinsey Institute after his death in 1955. The body of work residing at the Kinsey Institute remained largely unknown until it was made public and published later. The Kinsey collection represents one of the largest single collections of Lynes's work