R.J. Mitte's journey to stardom began in 2006 when he relocated to Hollywood, California, with his family to support his sister, actress Lacianne Carriere, in her pursuit of print and commercial work. To make new friends in his new city, Mitte started taking acting classes with Los Angeles talent manager Addison K. Witt in Sherman Oaks, California. Despite being surrounded by working actors, Mitte's primary motivation for acting was to build friendships with kids his age.
Witt and talent agent Debra Manners of the Daniel Hoff Agency encouraged Mitte to audition for commercials and TV shows, and he landed a spot on the popular Disney show Hannah Montana in 2006. Mitte's time on the show led to rumors of a romantic connection with the show's star, Miley Cyrus.
In 2008, Mitte was cast as Walt White Jr., a series regular with cerebral palsy, on AMC Network's Breaking Bad. Although Mitte has a mild case of the condition, he had to conduct extensive research and relearn many of the challenges he faced as a child to accurately portray the character. The Daily Advertiser, a Lafayette, Louisiana, newspaper, featured Mitte in an article, highlighting his hometown roots and successful start in Hollywood.