CLICK ON PHOTOS FOR FULL GALLERY
The 17-year-old star was spotted DJ-ing with Ellie and Katy at a star-studded afterparty hosted by Universal at Soho House.
The trio, who all wowed the BRITs crowd with their musical performances, hit the decks as they let their hair down with stars including Jessie J, Emeli Sandé, Lily Allen and Noel Gallagher.
New Zealand-born Lorde chose a sleek all-black ensemble for the annual music awards, while Katy glittered in a shimmering long-sleeved top and matching skirt.
Ellie, 27, who won British Female Solo Artist, swapped the pink Vivenne Westwood princess gown she arrived in for an edgy black dress with cut out, sheer panelling.
It was a big night for Auckland native Lorde, who described winning the coveted BRIT as a "priceless surprise".
"I'm still so new to getting awards," she said. "My brain feels like it's exploding every time it happens, so forgive me."
The Royals singer was up against tough competition in her category from Katy Perry, Janelle Monáe, Lady Gaga and Pink. But despite taking the crown, Lorde was sure to thank the singers in her acceptance speech.
"I didn't expect to win, you don't expect to win at all when you're up against Gaga and Pink and Katy Perry," she said. "Thank you to the strong, intelligent, inspiring women in this category."
Lorde and Ellie were not the only stars to win big at the BRITS. One Direction took to the stage not once but twice during the ceremony, scooping the Global Success Award and British Video Of The Year for Best Song Ever.
Arctic Monkeys were named Best British Group and won the award for MasterCard British Album of the Year, while Bastille were crowned British Breakthrough Act and David Bowie won Best Male Solo Artist.