Although both the Princess, 30, and her commoner beau are based in New York - with Madeleine currently working for the World Childhood Foundation - the couple will marry in traditional Swedish royal fashion the Royal Palace chapel in downtown Stockholm.
"We're planning everything to the last detail," Madeleine revealed. "We will have an afternoon wedding followed by dinner held out at Drottningholm Palace, which I am very happy about. Drottningholm Palace means a lot to me because I was born and grew up there."
In the exclusive interview, the Princess also revealed that she has her bridesmaids chosen and that wedding invitations will be sent out before April 1. She also admitted to struggling with the guest list. "It has been a difficult process when you want to invite everyone but unfortunately it's not possible."
Madeleine, who is fourth in line to the Swedish throne, became engaged to 38-year-old banker O'Neill last October. By marrying a non-noble, she follows the example of her older sister, Crown Princess Victoria, who wed personal trainer Daniel Westling in 2010. The royal nuptials are set for June 8.