Proceeds raised from the auction are going to the City of Joy Aid charity, which was set up by French author Dominique Lapierre, who said: "There are tears in my eyes," and she added:
"I am absolutely dumbfounded to believe that a piece of cloth which belonged to such a magical actress will now enable me to buy bricks and cement to put the most destitute children in the world into schools."
The dress was one of three made for Audrey Hepburn for one of her best-known roles, as the eccentric Manhattan socialite Holly Golightly in the 1961 film.
As dress worn by Marilyn Monroe to sing Happy Birthday to President Kennedy was sold for $1.15m (L583,000) back in 1999.
