The Hollywood star strips down in several sex scenes with co-star Jake Gyllenhaal but on one day of filming she got naked for no reason.
Speaking at the premiere of the movie in New York, the 28-year-old said: 'On the day I shot the scene where I have to remove my trench coat and be nude underneath I thought we were filming, but it turned out we were just rehearsing and I got unnecessarily naked in front of a lot of people, but hey, I just did my job.'
Although she seemed confident on set when she was nude, Hathaway says she felt really nervous.
But Jake, 29, had nothing but praise for Anne and recently said she had a natural 'rhythm' during the sex scenes.
In Love and Other Drugs Gyllenhaal stars as a pharmaceutical salesman who ends up bedding Anne's character.