She displayed a little more than she planned to at the world premiere of the latest Harry Potter film in London this week. Mail Online reported.
But Emma Watson has managed to make light of the wardrobe error which revealed her knickers to a crowd of thousands.
She laughed off the incident on U.S. television, saying: 'At least I was wearing underwear.'
The 19-year-old was grilled about the embarrassing episode by chatshow host David Letterman on the Late Show with Letterman.
He produced a picture of her adjusting the bottom half of her free-flowing vintage 1970s Ossie Clark dress - and inadvertently putting her knickers on display.
'Tell us what's going on here,' said a deadpan Letterman as he put a copy of the picture on his desk.
'I don't actually remember it happening.'
The actress, who plays Hermione Granger in the Potter films, appeared on the show to promote Harry Potter and the Half-Blood Prince, which is released in cinemas on July 15. It is the sixth film in the hugely successful series.
Miss Watson could be spending a lot more time in the U.S. in the future.
In a recent interview she revealed that she was interested in going to university in the country.
She said she had considered taking up a place at Cambridge after getting straight As in her A Levels, but was put off because of the interest her going there would generate.
'Cambridge is so high profile', she said. 'I definitely am attracted to [going to study] in the States for that reason.'