She's playing the role made famous by Julie Andrews in the 1965 movie – something that has some die-hard fans up in arms.
"I get hate Tweets and stuff like, 'You're not Julie Andrews!'" the American Idol winner tells Entertainment Weekly.
"I know I'm not Julie," Underwood, 30, says. "Nobody is and I would never pretend that I was … I know my place."
While some people might be unhappy, Underwood has support from Andrews, who says she's "a fan" of the Grammy winner.
"Fifty years later, it's time somebody had another crack at it," the 78-year-old told Zap2it. "I had the best time of my life doing it, and it did wonderful things for me. I think it's great that it's being done again, but doing it live must be so daunting Carrie."
Underwood is being joined by True Blood's Stephen Moyer and Private Practice star Audra McDonald in the live three-hour special, which is based on the original 1959 Rodgers & Hammerstein musical and airs Dec. 5 at 8/7c on NBC.