Barnett was born in San Antonio, Texas to Robert and Luetta Barnett. The Last Song (film) is his first appearance as a cast member in a major feature film. While attending high school, Barnett was a member of the Future Farmers of America or FFA as it is more commonly known. His FFA projects were highly successful and earned him enough money to help pay for his education. He earned the rank of Eagle Scout in his senior year, the highest rank attainable in the Boy Scouts of America. While filming The Last Song (film), Barnett also worked with acrobats, aerialists, and synchronized swimmers as a cast member in the Viva! Show at SeaWorld San Antonio. Barnett has four step-siblings and is a senior at the University of Texas at San Antonio majoring in nutrition and health.
^Alan, Rosenberg (2009-06-25). "SAG Letter" (letter|format= requires |url= (help)). Los Angeles, California: Screen Actors Guild. Screen Actors Guild. p. 1. "Dear Adam: Congratulations! Your recent employment as a Principal performer in Last Song on June 19, 2009 qualifies you for membership in Screen Actors Guild, the most distinguished performers' union in the world."|accessdate= requires |url= (help)