The 'Anna Karenina' star chose to marry her boyfriend James Righton in the pale pink designer frock, which she first wore at the pre-BAFTA party in 2009, because she wanted to get hitched in a gown with sentimental value.
She said: "It was something old, something new, something borrow and something blue. I had something old, which was the dress. But it's a dress that I've always had a brilliant time in. Every time I've worn it they've been brilliant nights. I wanted to be able to dance the night away and you can definitely dance in that dress."
Keira accessorised the dress with a jacket, a few bits of jewellery and a flowery headband.
She added: "The shoes and jacket were very beautifully designed by Karl Lagerfeld and made especially for me, so they were very new! I had my friend's ring for something blue and another friend's necklace for something borrowed."