Kennesaw Mountain National Battlefield Park Boundary Adjustment Act of 2012 - Modifies the boundary of the Kennesaw Mountain National Battlefield Park in Georgia to include approximately eight acres identified as the Wallis House and Harriston Hill on the map entitled "Kennesaw Mountain National Battlefield Park, Proposed Boundary Adjustment," and dated February 2010.
Authorizes the Secretary of the Interior to acquire land or interests, by donation or exchange, from willing sellers only.
Requires acquired lands and interests to be administered as part of the Kennesaw Mountain National Battlefield Park.