McEntire has chosen not to return to the awards gala after 14 years as one of the show's co-hosts, ACM spokesperson Bob Romeo has told The AP.
Romeo added that the ACM organisation "fully understand[s] and support[s]" McEntire's decision to focus on her new ABC sitcom Malibu Country.
It is not yet clear if Shelton will host the 2013 ACMs solo or if he will have a new co-host.
The 2013 Academy of Country Music Awards will be held next spring in Las Vegas.
Taylor Swift took home the 'Entertainer of the Year' award at the 2012 ceremony, with Shelton being named 'Male Vocalist of the Year' and Miranda Lambert taking 'Female Vocalist of the Year'.
Watch Reba McEntire's 'Fancy' music video: