Catherine attended the celebration to mark the opening of the new Treasures gallery at the museum where she turned heads with her fresh look.
The 30-year-old revealed a more layered and choppy style cut into her famous glossy mane than seen before.
Catherine also revealed newly cut bangs that were heavily parted to give a curtain effect slightly masking her face.
The colour was also notably darker than at her previous public appearances, and was reminiscent of the haircut she sported six years ago when publicity about her relationship with Prince William was rife.
Staying true to her passion for recycled fashion, Catherine completed her look by wearing a green silk Mulberry dress that she has previously been photographed in.
The style icon wore the dress a year ago at a reception at Buckingham Palace to launch Queen Elizabeth II's Jubilee celebrations.
Catherine added a pair of sensible black heeled shoes to complete her demure ensemble.
The Treasures gallery, which opens to the public on Friday, is a new permanent exhibition at London's famous museum.
Catherine spoke briefly at the event where she gushed about her memories of visiting the artefacts with her husband when they were dating.
"The Natural History Museum has a very special place in the heart of this nation," Catherine revealed. "William and I are just two of millions of people who have passed through these doors, and marvelled at the spectacular wonders of the natural world, housed in this beautiful gallery."
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