Asa Butterfield was born in Islington, London, the son of Jacqueline Farr and Sam Butterfield. He has an older brother, Morgan, who is a drummer for the English band "Oats," and a younger sister, Loxie
Butterfield first started acting at the age of 7 on Wednesday afternoons after school at the Young Actors Theatre, in his hometown. Later, he secured minor roles in the 2006 television drama After Thomas and the 2007 film Son of Rambow. In 2008 he also had a guest role playing Donny in Ashes to Ashes. He is well recognized for his distinctive blue eyes.
In that same year, he played the lead role in The Boy in the Striped Pyjamas. Director Mark Herman said that they came across Butterfield early on in the audition process. He was on the first audition tape he received and he was the third hopeful he met in person. Herman thought Butterfield's performance was outstanding, but only decided to cast him after auditioning hundreds of other boys, "so no stone was left unturned".
Producer David Heyman and director Mark Herman were looking for someone who was able to portray the main character's innocence, so they asked each of the children what they knew about the Holocaust. Butterfield's knowledge was slim and it was purposely kept that way throughout filming so it would be easier for him to convey his character's innocence. The final scenes of the film were shot at the end of the production period to prepare both him and Jack Scanlon for the dramatic ending of the film. He beat hundreds of boys to the role and also successfully passed the auditions for a role in Mr. Nobody for which he auditioned at the same time. He chose not to pursue the latter role.
In the 2008 Merlin episode "The Beginning of the End", he plays a young druid boy sentenced to death by Uther Pendragon because he feels threatened by the boy's magic. Despite the Great Dragon's advice and the warning that Arthur cannot survive if the boy does, Merlin and Arthur, with the help of Morgana, help the boy escape to rejoin the Druids. When they are about to disappear into the forest, Arthur asks him for his name, which he says is Mordred, an important character from the Arthurian legends who is supposed to kill King Arthur. Butterfield has appeared as Mordred in subsequent episodes.
In 2010, he appeared alongside Anthony Hopkins in The Wolfman. He starred as Norman Green in Nanny McPhee and the Big Bang (2010), working together with Emma Thompson. The film received positive reviews along with his performance. He subsequently played the main character, Hugo Cabret, in Martin Scorsese's new 3-D film Hugo, which was filmed from June 2010 to January 2011. It was released on 23 November 2011.