Alfie Allen was born in Hammersmith, London. He is the son of actor Keith Allen and producer Alison Owen and brother of singer and actress Lily Allen. He attended the Fine Arts College in Hampstead where he studied for his A-levels. Allen`s first on screen appearance was in a TV show You are Here (1998). He also made a brief appearance in Agent Cody Banks 2: Destination London (2004). Later, he starred in various movies like The Other Boleyn Girl (2008), Soulboy (2010) and The Kid (2010). In 2008, he replaced Daniel Radcliffe in a revival of Equus, but it was not until 2011, when he was cast as Theon Greyjoy in HBO's hit TV series Game of Thrones that he garnered international fame. His next release is John Wick, which is slated to release November 2014.

In 2018, he appeared alongside Boyd Holbrook and Trevante Rhodes in Shane Black's Hollywood action adventure and horror The Predator.