The actress – who's at the Utah fest with two movies, The Extra Man and The Romantics – arrived looking cute and cozy in the snow but without hubby Tom Cruise.
Holmes, 31, started her evening by heading to the Hotel Park City for dinner with pals before her The Extra Man premiere. "Katie arrived at Ruth's Chris Steakhouse," says a onlooker, "with five people – three girls and two guys.
"She sat a real great table in the middle of the restaurant. A lot of people knew who she was but no one really approached her. She seemed really comfortable and really calm – really seemed content," adds the eyewitness.
Per the Sundance style, Holmes kept the vibe cool. "She got up and walked around the restaurant by herself, no security or anything," says the onlooker. "The table shared a bottle of red wine. When she left they went out to the car they had waiting."
Also dining together in the steakhouse were Kerry Washington and Naomi Watts, stars of Mother and Child.
Following dinner, Holmes hit the red carpet for her premiere. In a white beanie and scarf combo she fit in perfectly with the causal festival look, and she posed for photographers along with costars Kevin Kline, Paul Dano and John C. Reilly.
On Tuesday, Holmes is expected to attend her second premiere, for The Romantics. The romantic comedy, which focuses on a group of college friends who reunite after 6 years for a wedding, features an all-star ensemble that also includes Josh Duhamel, Anna Paquin and Adam Brody.
With reporting by MARK GRAY