[Pictured: McGraw rehearses for the ACMs on Saturday]
The country star reportedly had a "major disagreement" with the show's producers and will not be performing on the show, according to Entertainment Weekly.
A rep for the country star told Access that EW's report on Sunday of the sudden change of plans was "accurate."
Access has learned that McGraw is still scheduled to perform at Monday's tribute concert to George Strait, who is being honored as Artist of the Decade.
The ACM Awards air tonight at 8 PM on CBS.
Related Content from AccessHollywood.com:
VIEW THE PHOTOS: CMT Music Awards 2008
PLAY IT NOW: On The Download: Dierks Bentley - 'Feel That Fire'
PLAY IT NOW: 2009 Grammy Awards Backstage: Carrie Underwood Talks Grammy Win