The Achievement in Costume Design Oscar was Jacqueline Durran's first win, although she's been nominated twice before - in 2006 for Pride and Prejudice and in 2008 for Atonement.
Coincidentally, all three of her nominated films have been directed by Joe Wright and starred Keira Knightly.
Durran's period costumes for Anna Karenina also took home awards at last week's Costume Designer Guild Awards and the BAFTAs earlier this month.
Although the film was set in the 1870s, Durran consulted the elaborate 1950s-era couture gowns of Christian Dior and Christobal Balenciaga for inspiration, and was largely favoured by the fashion industry to take home Oscar night's top costume prize.
The North London based designer said the win was "completely overwhelming" and paid tribute to her children who were "fast asleep in England".