Juno Violet Temple was born in London, England, into a showbiz family, the daughter of producer Amanda Temple and film director Julien Temple. She was named 'Juno' after her parents took a visit to the Grand Canyon during pregnancy and found they were standing on a butte of Cape Final known as Juno Temple. She has English and Scottish ancestry.

Her family moved to America, where she spent the first four years of her life. The family then moved back to England and settled in Somerset. At age four, she decided she wanted to be an actress after her father showed her La Belle et la Bête (1946) by Jean Cocteau.

She attended Enmore Primary School in Somerset. It was during this time that her father cast her in his film Vigo (1998). However, her father ended up cutting her out of the film. Two years later, at age 11, her father cast her in another of his films, Pandaemonium (2000).

She became a weekly boarder at King's College boarding school in Taunton. She then moved on to Bedales boarding school in Hampshire to take her A-Levels, one of which was Drama. She left with a B and two C's.

At age 15, she told her parents that she was serious about becoming an actress Her mother saw a call for an open audition for Notes on a Scandal (2006), and Juno was successful in winning the role of Cate Blanchett's daughter. This was her big break and led to a role in another high-profile film, Atonement (2007). She dyed her hair red to play Lola.

In 2009, Juno moved to Los Angeles, partly for her acting career.