The Australian actress dressed in a floor length white Givenchy gown at the Odeon Leicester Square.
From the front the dress appeared tobe a modest creation, long sleeved with a high neckline, but Blanchett turned to reveal the modern and fashionable cutaway back.
To break up the all white ensemble, her gown had two black straps added onto the shoulders.
The 43-year-old chose a small boxy clutch in white to complete her graceful and angelic appearance.
Hair and make-up was kept classic, with Blanchett opting for a casual pulled back hair style and neutral eye make-up tones.
Blanchett, who plays elf queen Galadriel in The Hobbit: An Unexpected Journey, was joined by her cast mates on the green-coloured carpet for the premiere.
