Earles played the older brother of Miley Stewart (Miley Cyrus), Jackson Stewart, in the Disney Channel Original Series Hannah Montana. He guest starred twice on Phil of the Future as Grady Spaggett, an advanced math student. Earles was in the 2006 Disney Channel Games on the Blue Team and in the 2007 and 2008 Disney Channel Games on the Red team.
Earles played a nerdy card gamer who was friends with the character Brian Miller on the sitcom Still Standing. In 2004, he appeared in the movie National Treasure as Thomas Gates, ancestor of Ben Gates (Nicolas Cage). In 2005, Earles played Ernie Kaplowitz in the movie American Pie Presents: Band Camp. Earles also plays Hunter, the android protector of the main character, in the new Disney XD series Aaron Stone. He also voiced Spudnik in the talking dog movie, Space Buddies.
Earles was the co-host of Disney Channel's Sing-Along Bowl-athon (Disney Channel's 2006 New Year's Eve special) and the corresponding online voting. Jason stars in the Disney XD Original Series Kickin' It, premiered on 13 June 2011.
In 2005 Earles started dating a women named Linda. He announced their engagement on May 21, 2008. The couple got married on September 23, 2008. Their first son Justin, was born on August 29, 2010. Their second son was born on April 23, 2012.