Bradbery, who was coached by fellow country singer Blake Shelton, covered her mouth and began to cry when named the winner, hugging runner-up Michelle Chamuel.
"I'm so thankful," the 16-year-old Texan said. "I'm sorry, I'm speechless."
Bradbery, who said she had never had a singing lesson before the show, rode Sara Evans' country hit "Born to Fly" and Carrie Underwood's "All-American Girl" to victory, becoming the youngest winner of the NBC singing competition in its fourth season.
She topped pop-rock singer Chamuel, who was coached by R&B singer Usher, and third-place finishers the Swon Brothers, country-rock singers Colton and Zach Swon, who were also coached by Shelton.
It was the third consecutive win for Shelton, a mainstay atop the U.S. country charts with song like "Who Are You When I'm Not Looking" and "Drink on It."
Cher performed "Woman's World," a new single from her album of the same name which is to be released in September, the Grammy-winning singer's first in 12 years.
Aguilera, who will be returning to the show for the fall season, opened the show joining rapper Pitbull in their hit song, "Feel This Moment."
Contestants eliminated earlier in the season also performed on Tuesday's finale and Monday's penultimate show.
Its fifth season will begin in the fall with former coaches Aguilera and CeeLo Green returning to replace first-time coaches Shakira and Usher, who will return for season six.