The ultra-sexy ensemble looked like a white bra top and high-waisted shorts in the front, but featured a short, sleeveless pink-embroidered lace overlay in the front to make it a dress. Stewart wore her long brunette locks up in a messy ponytail.
The Twilight beauty posed with her fellow On the Road costars Sam Riley, Kirsten Dunst and Garrett Hedlund. Dunst, 30, styled a more conservative navy blue Dior dress, while her real-life boyfriend Hedlund, 28, and Riley, 32, looked handsome in Gucci and John Varvatos suits.
With three major films to promote in 2012, Stewart has been stepping up her red carpet style this year, and was asked by reporters to pick a favorite red carpet look. "I've liked everything I've gotten to wear this year, I think!" she said. "I don't want to offend any of the dresses."
But true to her style, Stewart changed into a leather jacket, gray shirt, jeans and boots after she walked the carpet.
Stewart skipped watching the screening of the film and enjoyed a private dinner instead with Dunst at Abe & Arthur's in NYC's Meatpacking District before heading over to the official after party at The Standard Hotel.
Indulging in cocktails and hors d'oeuvres while the bands Cole Ramstad and Chinatown All Stars played, "Kristen was in good spirits and mostly spent the night at Sam Riley's side," a witness tells Us Weekly.
But the costars all went up to the roof for smoke break together. A source tells Us that Hedlund and Dunst, who began dating in January, seemed more in love than ever -- with Dunst sitting on Hedlund's lap.