The royal family would pay for all the core elements of the wedding including the service, flowers and music.
Harry's communication's secretary Jason Knauf said Windsor was a "very special place" for Harry, and that he and Markle had spent time there together during their 16-month romance.
"In these beginning few months and now being boots on the ground in the United Kingdom, I'm excited to really get to know more about the different communities here and smaller organizations that are working on the same causes that I've always been passionate about", she added.
They are grateful to the Queen for granting permission for the use of the chapel.
"They will be making sure it reflects who they are as a couple", he said.
Mr Knauf revealed that while one of Ms Markle's beloved dogs Guy was legally allowed to stay with her in the United Kingdom, the other - Bogart - would not be joining her.
Bogart, had been rehomed with friends at an undisclosed location - presumably in Canada or the United States.
There will also be a walkabout by the bride and groom-to-be - a royal rite of passage for the future royal.
The actress will not be continuing her work on gender with the United Nations or with other organisations, but instead will be starting her charity work as a full-time royal afresh.
The exact date has not yet been revealed.
Prince Harry and his fiancee also hope to allow members of the public to feel part of the celebrations and are considering how to make that happen.
Instead, they have opted for the lower-key choice of St George's Chapel at the Windsor Castle royal estate west of London.
But Middleton's wedding, for example, drew a crowd of a million stretching from the abbey to Buckingham Palace, not to mention the 5,000 street parties that took place elsewhere across the United Kingdom. Prince Charles and Camilla Parker-Bowles had a televised religious blessing there after they had a civil wedding ceremony nearby in 2005.