The collection has been based at Althorp House, the Spencer family's Northamptonshire home, since July 1998 - a year after the former wife of Prince Charles died in a car crash in Paris, aged 36.
The exhibition features more than 150 personal objects, including her Emanuel wedding dress.
A spokesperson for her brother, Earl Spencer, said it had been a "celebration" marking Diana's "charitable works and glamour" and had helped raise more than 1.2 million pounds to help disadvantaged people around the world.
Born Diana Spencer at Park House near Sandringham, Norfolk, in July 1961, she became Lady Diana Spencer after her father inherited the title of Earl Spencer in 1975.
More From This Section
Diana moved to Althorp House in 1976 and was said to love the grounds and house, which was bought by her ancestor Sir John Spencer in 1508.
The exhibition has been open to the public throughout July and August since July 1998, which marked her 37th birthday.
Meanwhile, a 1994 Audi 2.3 E convertible once owned by the Princess of Wales will be one of the star lots at an auction at Blenheim Palace in Oxfordshire on June 29.
The Audi was the family car in which Diana was photographed on a number of occasions driving her sons Princes William and Harry in 1994.
Until the auction, the 2.3-litre-engined car is on display at the Grange St Paul's Hotel in London.