Born in London, England, Hayley Elizabeth Atwell has dual citizenship of the United Kingdom and the United States. An only child, Hayley was named after actress Hayley Mills. Her parents divorced when she was age two. Her father returned to America and Hayley remained with her mother in London, but she spent her summers in Missouri with her father. Hayley's mother saw theater as an important communal experience, so she was introduced to theater from a young age.
Atwell also starred in Cassandra's Dream (2007), The Duchess (2008), Cinderella (2015) and Black Mirror episode Be Right Back. In 2011 she was nominated for an Golden Globe for her work in The Pillars of the Earth.