An anonymous bidder bought the dress suit, by British designer Mansfield, at a Christie's auction in London late Monday.
Separately, a buyer in South Korea snagged six other striking outfits on auction, all of which were worn by Thatcher in the 1970s before she became prime minister.
Those outfits included a canary yellow dress with navy trim and a matching jacket that the former leader wore to the Conservative Party Conference in 1975; a blush pink outfit Thatcher wore in a BBC show in which she was interviewed about her skin care regime; and a silver and gold cocktail ensemble.
In total, the outfits fetched a little more than 73,000 pounds - far exceeding the initial estimates of 1,000 to 1,500 pounds for each outfit.
The sales were part of a "London" themed auction that included royal, Olympic and political memorabilia.