Beaton was born on 14 January 1904 in Hampstead, north London, the son of Ernest Walter Hardy Beaton (1867–1936), a prosperous timber merchant, and his wife, Esther "Etty" Sisson (1872–1962). His grandfather, Walter Hardy Beaton (1841–1904), had founded the family business of "Beaton Brothers Timber Merchants and Agents", and his father followed into the business. Ernest Beaton was an amateur actor and met his wife, Cecil's mother Esther ("Etty"), when playing the lead in a play. She was the daughter of a Cumbrian blacksmith named Joseph Sisson and had come to London to visit her married sister.
Ernest and Etty Beaton had four children – Cecil; two daughters, Nancy Elizabeth Louise Hardy Beaton (1909–99, who married Sir Hugh Smiley) and Barbara Jessica Hardy Beaton (1912–73, known as Baba, who married Alec Hambro); and son Reginald Ernest Hardy Beaton (1905–33).
A 1932 Standard Rolleiflex, a type of camera used by Beaton
Cecil Beaton was educated at Heath Mount School (where he was bullied by Evelyn Waugh) and St Cyprian's School, Eastbourne, where his artistic talent was quickly recognised. Both Cyril Connolly and Henry Longhurst report in their autobiographies being overwhelmed by the beauty of Beaton's singing at the St Cyprian's school concerts.
When Beaton was growing up his nanny had a Kodak 3A Camera, a popular model which was renowned for being an ideal piece of equipment to learn on. Beaton's nanny began teaching him the basics of photography and developing film. He would often get his sisters and mother to sit for him. When he was sufficiently proficient, he would send the photos off to London society magazines, often writing under a pen name and "recommending" the work of Beaton.
Beaton attended Harrow School, and then, despite having little or no interest in academia, moved on to St John's College, Cambridge, and studied history, art and architecture. Beaton continued his photography, and through his university contacts managed to get a portrait depicting the Duchess of Malfi published in Vogue. It was actually George "Dadie" Rylands – "a slightly out-of-focus snapshot of him as Webster's Duchess of Malfi standing in the sub-aqueous light outside the men's lavatory of the ADC Theatre at Cambridge."Beaton left Cambridge without a degree in 1925.