"I thought I was just coming here to present an award," Timberlake told the audience. "I get to take one home."
Tim McGraw took home the Artist of the Year in the country music category, while Michael Jackson was also on hand to take home the Humanitarian Award. Casey Kasem received the Radio Icon Award.
The highlight of the evening, however, was Tom Petty and the Heartbreakers being honored with the Legend Award.
Stevie Nicks presented the award to the group in front of thousands of cheering fans. "He not only started out as my greatest musical influence, but today he's still my greatest musical influence," Nicks said.
The group performed two songs, "I'm Crying" and "Runnin' Down a Dream." Petty thanked radio stations for taking a chance on an "unknown band."
The awards are based on radio's top-playing songs and voted on by radio program and music directors nationwide.