The 35-year-old actress dismissed reports of a romance with Pitt on Tuesday while attending a New York screening of her movie The Lost City of Z.
"I'm not even going to dignify it with a response. It's predictable and silly," she told Page Six.
Page Six had reported Monday that Miller and Pitt were doing some "serious flirting" after the film's Los Angeles premiere last week. Miller stars as Nina Fawcett in the movie, which was produced by Pitt's Plan B Entertainment company.
"[They were] heavily enjoying each other's company [and] were talking to each other all night," a source said.
Insiders told E! News the dating rumors were "exaggerated." Miller split from partner Tom Sturridge in 2015, while Pitt's wife, actress Angelina Jolie, filed for divorce in September after two years of marriage and a decade together.
"It was a very difficult time," Jolie said in an interview with the BBC in February. "We are a family, and we will always be a family. We will get through this time and hopefully be a stronger family for it."
Miller shares daughter Marlowe with Sturridge, while Pitt is dad to six children, Maddox, Pax, Zahara, Shiloh, Vivienne and Knox, with Jolie. The Lost City of Z co-stars Charlie Hunnam and Robert Pattinson, and opens in theaters Friday.