After being in Los Angeles for a short time, Rathbone was cast in Disney 411, where he interviewed up-dan-coming personalities like Hilary Duff dan the sister duo Aly & AJ. He has also had guest roles on The O.C. dan Close to Home. His film roles include work in Molding Clay, Pray for Morning, dan Travis dan Henry. In 2005, he scored the role of Nicholas Fiske in ABC Family's original series Beautiful People. In a 2008 interview, he stated it was his first leading man role dan was his most difficult role to fit into.[9]

In 2008, beliau memainkan Jasper Hale dalam filem Twilight, berdasarkan novel jualan terbaik karya Stephenie Meyer.[10] He reprised his role in dalam sekuel kepada Twilight, The Twilight Saga: New Moon, The Twilight Saga: Eclipse dan The Twilight Saga: Breaking Dawn.[11][12] In 2009, Rathbone played Jeremy in S. Darko. In addition to that role, he won kudos for his performance as a serial killer on Criminal Minds. Rathbone memainkan watak Sokka dalam The Last Airbender, sebuah filem 2010 berdasarkan siri beranimasi.[13] The Last Airbender telah menyebabkan kontroversi disebabkan pemilihan pelakon putih seperti Rathbone untuk memainkan watak yang difikirkan sesetengah penggemar sebagai depictions of Asians or Inuit. Rathbone berkata, "I think it's one of those things where I pull my hair up, shave the sides, dan I definitely need a tan. It's one of those things where, hopefully, the audience will suspend disbelief a little bit."[13]

Variety reported Rathbone would soon star in an upcoming indie film drama, Truckstop which will begin filming in September. Rathbone will be playing the role of Charles, "a man with cerebral palsy who takes care of his dying father while working at truckstop, where he befriends a troubled young prostitute."[14]Rathbone appeared in an episode of No Ordinary Family on November 9, 2010.[15][16]

Rathbone was recently cast as the lead in a new upcoming teen action series, Aim High. He will portray the role of Nick Green, a high school junior who's just starting a new school year as one of the country's 64 highly trained teenage operatives. Filming took place in November 2010 dan the series is slated to premiere in 2011.[17]