The company will extend its portfolio to the two US cities, it has revealed.
Nashville Comic Con will be held on October 18-20, 2013.
Its guests will include Stan Lee, Dean Cain, James Marsters, Ernie Hudson and Billy Dee Williams.
Ale Garza, Michael Golden, Mike Grell, Greg Horn, Arthur Suydam and Renee Witterstaetter have been announced for the St Louis event, which will run from March 22-24.
The London-based Kapow! Comic Convention - which is fronted by Mark Millar - recently announced that it will be put on hold rather than making 2013 its third year.
Wizard World also operates conventions in Portland, Philadelphia, Chicago, Ohio, Austin and New Orleans.