In a statement released through Perez Hilton, the two acts said that due to demand for the first round of NKOTBSB dates, they were happy to add the additional shows from June 2011.
The groups said: "We can't thank our fans enough for their continued support. The love that everyone has shown to us and to this project is incredible.
"We can feel the excitement and we won't let the fans down. And with our new and elaborate stage design there won't be one bad seat in the house.
"We are truly blessed and are so appreciative to have you all along with us for the ride."
Full tour details are available at the NKOTBSB website. Tickets go on sale December 11 at 10am EST.