In 1959, Bailey became a photographic assistant at the John French studio. In May 1960, he was a photographer for John Cole's Studio Five, before being contracted as a fashion photographer for British Vogue magazine later that year. He also undertook a large amount of freelance work.
Along with Terence Donovan and Brian Duffy, Bailey captured and helped create the 'Swinging London' of the 1960s: a culture of fashion and celebrity chic. The three photographers socialised with actors, musicians and royalty, and found themselves elevated to celebrity status. Together, they were the first real celebrity photographers, named by Norman Parkinson "the Black Trinity".
The film Blowup (1966), directed by Michelangelo Antonioni, depicts the life of a London fashion photographer who is played by David Hemmings, whose character was inspired by Bailey. The "Swinging London" scene was aptly reflected in his Box of Pin-Ups (1964): a box of poster prints of 1960s celebrities including Terence Stamp, The Beatles, Mick Jagger, Jean Shrimpton, P. J. Proby, Cecil Beaton, Rudolf Nureyev and East End gangsters, the Kray twins. The Box was an unusual and unique commercial release. It reflected the changing status of the photographer that one could sell a collection of prints in this way. Strong objection to the presence of the Krays by fellow photographer, Lord Snowdon, was the major reason no American edition of the "Box" was released, and that a second British edition was not issued. The record sale for a copy of 'Box of Pin-Ups' is reported as "north of £20,000".
At Vogue Bailey was shooting covers within months, and, at the height of his productivity, he shot 800 pages of Vogue editorial in one year. Penelope Tree, a former girlfriend, described him as "the king lion on the Savannah: incredibly attractive, with a dangerous vibe. He was the electricity, the brightest, most powerful, most talented, most energetic force at the magazine".
American Vogue's creative director Grace Coddington, then a model herself, said "It was the Sixties, it was a raving time, and Bailey was unbelievably good-looking. He was everything you wanted him to be – like the Beatles but accessible – and everyone went in when he went on the market. We were all killing ourselves to be his model, although he hooked up with Jean Shrimpton pretty quickly".
Of model Jean Shrimpton, Bailey said:
She was magic and the camera loved her too. In a way she was the cheapest model in the world – you only needed to shoot half a roll of film and then you had it. She had the knack of having her hand in the right place, she knew where the light was, she was just a natural.