The Victor Edelstein, off-the-shoulder design, in midnight blue velvet was successfully snared by an anonymous bidder who said he wanted to surprise his wife.
The Princess of Wales wowed both the British and US public when she was pictured being twirled around the dancefloor by the Hollywood star during the 1985 US visit.
Auctioneer Kerry Taylor said: "It was bought by a British gentleman who said he wanted to buy it as a surprise to cheer up his wife. I hope that the sale has really made someone's day."
The dress was one of 10 of Diana's dresses on sale as part of the Fit For A Princess collection at the vintage fashion auctioneers Kerry Taylor Auctions in London.
The garments were originally sold, along with a number of others, by Diana herself following her divorce from the Prince of Wales to raise money for charity at the suggestion of Prince William.
American Maureen Rorech Dunkel initially bought the dresses as a long-term investment, but after Diana's death in 1997 she decided to exhibit them to raise money for good causes.
The collection, described as "a little history of Diana's life through her clothes", reached a total of £862,800.
The other dresses that sold were:
:: A black velvet and beaded Catherine Walker evening gown, in which Diana was photographed by Mario Testino for a Vanity Fair photoshoot at Kensington Palace a few months before her death, sold for £108,000.
:: A Catherine Walker dress, a burgundy crushed velvet evening gown worn for a state visit to Australia in 1985 sold for £108,000.
:: A Catherine Walker embroidered pink silk evening gown and bolero which was made for Diana and Prince Charles's state visit to India in 1992 was sold for £66,000.
:: A Catherine Walker burgundy velvet gown with embroidered tailcoat worn during a state visit to Korea in 1992 sold for £50,400.
:: A Bruce Oldfield black velvet evening gown, worn for an official portrait by Lord Snowdon in 1985, sold for £50,400 to a British museum.
:: A pink sequinned crepe dress by Catherine Walker, worn on a state visit to Brazil in 1991, sold for £78,000 to the same museum.
:: A sequinned sea-green Catherine Walker evening gown, worn for a state visit to Austria in 1989, sold for £90,000 to an Austrian bidder.
:: A white chiffon cocktail dress by Zandra Rhodes, worn to the Birthright benefit event at the London Palladium in 1987, was sold for £48,000.
:: A bottle green Victor Edelstein dress, which Diana wore for private entertaining was sold for £24,000.
Miss Taylor said: "Diana was the people's princess, so the people should be able to see these dresses. This is our heritage, our history."