Guarini’s vocal talents were recognized at the early age of four, when he became the youngest member of the Atlanta Boys Choir, developing his voice listening to everything from jazz to R&B and rock. Instead of focusing solely on his vocal abilities, Guarini went on to college in Philadelphia where he studied a range of performing arts, later moving to New York to continue to expand his skills in theater. Within a few months, he was approached to join the cast of the Broadway production of “The Lion King,” but chose not to take the role. He worked out in master classes for the production.
Guarini’s mother told him about the TV advertisement for “American Idol.” Weeks later, Justin joined over 1,000 other young hopefuls in New York. Once Justin joined the “American Idol” competition, he quickly moved through the ranks. When the show hit the air, Justin immediately moved to the front with a show-stopping performance in week #3. Although he didn’t win the title, Guarini was immediately signed by 19 Entertainment and a global recording deal with RCA, and he was cast in his first leading role in the hastily assembled 2003 film "From Justin to Kelly," a musical romp in the mold of "Grease" and the "Beach Blanket Bingo" films.