Diaz defeated three other finalists Virgil Gadson, JaJa Vankova and Hailee Payne in the finale, which took place on September 14, reported E! Online.
Besides the title, she gets prize worth USD 250,000 and the opportunity to dance in pop star Jennifer Lopez' Vegas residency.
During the two-hour live finale, Jenna Dewan-Tatum performed with former-contestant-choreographer Travis Wall.
Diaz is the first tapper to win the title of America's favourite dancer.