The 29-year-old looked chic in the fitted mini dress, which was covered in jewels and contrasted with a white Peter Pan collar.
Keeping accessories to a minimun, Katy wore a green gemstone ring and kept her long black locks flowing either side.
Although she was there to promote Prism, Katy was also celebrating her social status as the most popular Twitter user, after knocking off Justin Bieber from the top spot. Katy now has an astounding 45.5 million followers!
Katy, who is dating musician John Mayer, later made funny hand gestures towards the crowd, as she stood in front of two large boards with her album artwork on.
The 'Roar' singer has also been embracing the culture and posted a photo of herself to Twitter this morning, dressed in traditional Japanese gear.
Katy looked elegant as she wore a black kimono with pink roses printed on it. The popstar, who tied her hair back into a ponytail, raised her two hands to her mouth.
Captioning the photo, she cryptically said: "One of these things is not like the others..."
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Watch Katy's 'Roar' video below: