Alex Pettyfer was born in Stevenage, Hertfordshire, the son of Lee Ireland, an interior decorator, and Richard Pettyfer, an actor. He has a younger half-brother, James Ireland, a junior tennis player, from his mother's re-marriage to Michael Ireland, a property developer.
Alex Pettyfer was raised in Windsor, and began his career as a child fashion model at the age of seven, for Gap, after meeting Ralph Lauren in a toy store in New York City. He also did advertisements for some yogurt brands. His first commercial was at age six.
As a schoolboy, he performed in plays, including in the role of Willy Wonka in a production Charlie and the Chocolate Factory. Alex Pettyfer was educated at two junior independent schools: The Mall School, a small school in Twickenham, followed by the Lambrook Haileybury school in Berkshire.. He subsequently attended two other independent boarding schools: Millfield School in Street in Somerset and Shiplake College near Henley-on-Thames in Oxfordshire. After his GCSEs, he left Shiplake College to attend the independent Sylvia Young Theatre School