The windmill slam earned the wild applause of the sold-out crowd at the Toyota Center and lifted the 22-year-old rookie to the title over Jeremy Evans of the Utah Jazz.
"I feel blessed, but it's still overwhelming," he told reporters. "I'm just trying to soak it all in."
Ross garnered 58 percent of the votes from the public in the two-dunk championship round to claim the title.
In another skills test, second-year guard Kyrie Irving of the Cleveland Cavaliers defeated San Antonio Spurs power forward Matt Bonner 23-20 to win the three-point shooting contest.
Ross said he never dreamed he would win the title.
"It was my favourite event to watch every year, since I was a small child," he said. "But actually winning it, I never thought I'd do it. It's been unbelievable. I've had fun."
In the opening round of the finals, Evans leaped over a covered easel and delivered a left-handed windmill slam. After the dunk, he pulled the cover off the easel and revealed a picture of himself dunking the ball.
He then signed the picture to the roar of the crowd.
But Ross clinched the competition with his gravity-defying leap over the ballboy, who also needed a leap of faith that he was not going to get clobbered.
"I told him the day before that I was going to jump over him, but I never told him I was going to go through the legs," said Ross. "He was kind of nervous.
"When I first grabbed him he said, 'You're not going to hit me, right?' I said, 'No, I'm not going to hit you.' So I had to calm his nerves."
In the three-point contest, the 20-year-old Irving, who is also playing in Sunday's All-Star game, said he was using the occasion to become better known because the Cavaliers are generally out of the national spotlight.
"This weekend was just basically about earning everybody's respect and getting a chance to people to see me that don't usually see me," he said. "We're not nationally televised.
"This weekend is to get everybody acclimated to my face."
- Sports & Recreation
- Kyrie Irving
- Jeremy Evans