Camilla becomes a septuagenarian on Monday and celebrated with two parties over the last week.
The picture, which was taken in May, was captured by celebrity photographer Mario Testino at Clarence House.
The Prince of Wales and Duchess of Cornwall will return to their duties in Devon and Cornwall later in the week.
Camilla is wearing a smart navy coat dress by one of her most trusted designers, Fiona Clare, with her favourite pearl choker and earrings.
Family portrait: Testino was also invited to take this photograph for Princess Charlotte's Christening.
Later on Saturday, a birthday party for the Duchess will be staged at the Prince's Highgrove home in Gloucestershire, with a large gathering expected at the private event.
Charles, who will celebrate his 70th birthday next year, is meanwhile, in a British wool suit, light blue tie and pocket handkerchief.
He added: "I'm honoured to document their royal highnesses the Prince of Wales and the Duchess of Cornwall on this very important date". The photographer also added that in 2006, at their first meeting, he had discovered "a person is attractive and generous, with a wonderful sense of humor". "But behind closed doors she appears to have provided the heir to the throne with the love and a normal life, away from his public role, that he has always wanted", the newspaper said in a short biography written for Camilla's birthday.
It followed a reception at Clarence House, which had an even more star-studded guest list - actors Dame Maggie Smith, Joanna Lumley and Richard E Grant were present, as was Australian author Kathy Lette.
That's what a lot of fans can't help but wonder as the Duke and Duchess of Cambridge's names seemed to be left of the guest list of Camilla's party.