The cameo will mark Obama's second appearance at the awards ceremony after his stint in 2008 with Hilary Clinton and John McCain.
CMT's President Brian Philips said in a statement: "The President and Governor Romney each understand the reach of the CMT audience, particularly on our highest-rated night of the year.
"They're each great sports, they're 'in on the joke', and they each went out of their way to deliver great moments for CMT."
The CMT Music Awards, which recognise the top performers in the country music genre, will include appearances from Carrie Underwood, Lady Antebellum, Toby Keith, Kenny Chesney and Willie Nelson.
Hosted by Keith and Kristen Bell, the show will air live on Wednesday night (June 6) at 8pm ET on CMT and CMT.com.
Watch the promo for the 2012 CMT Music Awards below: