Speleers was born at St Richard's Hospital, Chichester, West Sussex. His parents divorced when he was three. His mother, Gill, lives in Spain; his father, John, is a financial consultant and lives in London. He has two older half brothers. In 2006, he left Eastbourne College to portray Eragon. Before starring in the film Eragon, he had already auditioned for a number of roles, such as Peter Pevensie's The Chronicles of Narnia: The Lion, the Witch and the Wardrobe - which he lost to William Moseley. For Eragon, he defeated about 180,000 candidates.