Pettyfer began his career as a child fashion model at the age of seven, 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. He attended The Mall School, a small private school in Twickenham and as a schoolboy performed in plays, including in the role of Willy Wonka in a production Charlie and the Chocolate Factory. He then went on to attend Lambrook Haileybury school in Berkshire.

In 2005, Pettyfer, after ending his modeling career, made his professional acting début in the British television production of Tom Brown’s Schooldays, playing the lead character, Tom Brown; he received positive reviews for the role. In June 2005, he was cast in his most prominent role so far, that of teenage MI6 spy Alex Rider in the film Stormbreaker, based on the novel by Anthony Horowitz. He was one of 500 who auditioned for the role. Pettyfer chose to appear in the film over a role in the film Eragon, noting that he preferred Stormbreaker because it would be filmed in Britain, in the Isle of Man, while Eragon would film in the Czech Republic; Pettyfer is afraid of flying, and he liked the looks of the cast for Stormbreaker. Stormbreaker was released on 21 July 2006 in the United Kingdom, on 6 October 2006 in the United States and on 21 September 2006 in Australia.

One review of Pettyfer’s performance described him as playing the role with an “earnest intensity”, although another noted that he “isn’t quite at ease as an actor”. Media reports specified that the film was expected to make Pettyfer a “teen idol”. Pettyfer will not reprise the role if there is another Alex Rider film because he is too old.

He next appeared in Wild Child, a movie set in California and Yorkshire. He played school boy Freddie Kingsley and he co-starred with Emma Roberts. He will star in the film Beastly, based on the novel by Alex Flinn, alongside Mary-Kate Olsen, Vanessa Hudgens and Neil Patrick Harris which released in 2010. He finished filming on 13 August 2009, according to the film’s Twitter account.

Pettyfer returned to modelling in 2007. His recent modelling jobs include ad campaigns for Burberry in 2008 and 2009.

Pettyfer will be portraying one of the main characters of Unbound Liason alongside Sinthiya Sivarajah. Empty is an independant film set in New York and London.Filming is situated to begin in early april and carry through to june.

It has been announced that Pettyfer will be portraying the main character in I am Number Four, to be released in 2011. It will be co-starring Sharlto Copley , directed by D.J. Caruso, produced by Michael Bay and Steven Spielberg will be the executive producer.