HOUSTON -- Terrence Ross had to settle his nerves at the start of the All-Star dunk contest. By the end, he was calming down a ball boy he needed as a prop for his winning slam.

The 6-foot-6 Toronto rookie leapfrogged Michael Costolo, the son of Twitter CEO Dick Costolo, whipped the ball between his legs and hammered home a one-handed dunk to beat defending champion Jeremy Evans in the climax to All-Star Saturday.

Terrence Ross threw down a one-handed slam to beat defending champ Jeremy Evans and earn top honors in the slam dunk contest. Brett Davis/USA TODAY Sports

"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," Ross said. "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.' "

Ross seemed to be unsure of himself in the beginning, botching his first three dunk attempts in the first round. The crowd exploded when he finally pulled it off -- flicking the ball behind his back on the way up and hammering home a one-handed dunk.

He earned a perfect 50 and immediately relaxed.

"This is honestly my first really big dunk contest, so I was nervous," said Ross, the eighth overall pick in last year's draft out of Washington. "And not making a dunk didn't make it easy. I had to get myself together."

Ross earned 58 percent of the fan vote in the championship round, outdoing Evans' prop-filled display. Evans leaped over a painted portrait of himself and earlier former Jazz giant Mark Eaton, who sat on a box and held up the ball for Evans to swipe on his way to the rim.