The city of Chicago gave the team permission to make the changes on Thursday. The moves were done despite Wrigley Field's landmark status.
Peter Scales of the city's Department of Planning and Development said the changes were approved because "landmark buildings aren't frozen in time, need to be maintained and can be improved while respecting their history."
The changes were approved as Illinois Gov. Rod Blagojevich and Chicago mayor Richard Daley consider the Tribune Co.'s request to have the Illinois Sports Facilities Authority acquire and renovate Wrigley Field.
In addition to the seats, which will be called "Bullpen Box Seats," the club will be extending digital signage on the sides of the grandstands, according to Cubs vice president Mike Lufrano.
The Cubs currently have 82 Bullpen Box Seats along the first-base line. The team determined it had space for the new seats along the third-base line after the new drainage system was installed this offseason.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.