Bieber, 16, said the E! reality star, 29, was the person he most wanted to meet -- and he did.
He shook hands with her and talked to her for several minutes. They put their arms around one another, took out their phones and took pictures of themselves posing together.
After they posed, Kardashian Twittered that she officially had " Bieber fever." He then called her his "girlfriend."
A short time later, Ryan Seacrest Twittered to Bieber" Now she wants to know are you guys really dating? Ha"