We're used to seeing the actress dressed down while out with boyfriend Ashton Kutcher, but she pulled out all the stops in a chic dress at the New York-based event.
Gorgeous Mila looked even more stunning than usual in her blue and white frock, which featured a striped A-line skirt, demure knee-length hemline and a pretty strapless top.
The starlet cut an elegant figure in black pointed courts, adding a dazzling statement bracelet and a fresh nude manicure.
She wowed in the hair department too, slicking her long brunette locks in a straight, glossy style which emphasised her face-framing layers.
For her make-up Mila stuck to what she knew best, rocking her usual thick black eyeliner, bronzed cheeks and a peachy pout.
Mila is the ambassador for Gemfields, which champions itself on sourcing rare, colourful gemstones ethically.
Campaign shots of the actress were also on show at the launch and she looked beautiful with bold brows and subtly-defined eyes, plus messy fuss-free hair.
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