Baby, she’s a firework.

Katy Perry performed at the star-studded re-opening of New York City’s Tiffany & Co. flagship store Thursday, draped in a double-strand diamond necklace.

The “American Idol” judge took the stage wearing a Tiffany blue Givenchy gown with a sheer bottom and a bow in the back.

Perry, 38, paired the strapless gown with Givenchy G Chain Cube Sandals ($995) and the brand’s blinged-out Mini Kenny Bag ($3,800).

She sang “Firework,” “Dark Horse” and “Teenage Dream” during the surprise performance.

“Now look at me I’m sparkling,” Perry captioned a series of glam photos on Instagram after the event.

The appearance comes after the pop star was accused by “American Idol” viewers of being disrespectful toward contestant Wé Ani after her favorite singer, Elijah McCormick, was eliminated.

Rather than offering Ani feedback on her performance, Perry said she was “shook by the results” of the recent elimination, adding, “America, you guys have the votes. You’re the ones voting and if you’re not voting, you’re not using your voice. Your faves aren’t safe. So from now on, vote for who you want to see in the Top 12.”

And this month, Perry was booed by the “AI” audience after criticizing contestant Nutsa Buzaladze’s glittering outfit earlier.

After Buzaladze performed in a sparkling silver dress and boots, Perry told her, “Nutsa, every time you take the stage it’s like you glitter bomb the stage.”

“Listen, one thing that I would like to see from you is not one piece of glitter the next time. I know that is going to be hard,” she continued at the time.

For more Page Six Style you love …

In March, Perry was also criticized for making a “mom-shaming” joke about a 25-year-old contestant with three children. 

Perry quipped, “Honey, you’ve been laying on the table too much,” which offended the contestant and some viewers.