Katy wore a gorgeous, floor-length Oscar de la Renta dress, covered in white polka dots and pretty pink and red flowers. And always bang on it with the detailing, her nails blended in so well we almost missed them!
Opening the evening with her latest single 'Unconditionally', Katy joined the likes of Rihanna, Miley Cyrus, Taylor Swift and Jennifer Lopez at the Nokia Theatre for this year's prestigious event.
And we loved her arrival outfit – literally from top-to-toe.
Not only was her dress a total winner, but it was topped off with beautiful, classic make-up; soft, elegant curls and her nails were, er, spot on!
What's great about Katy's latest manicure is that it's a total cinch to copy.
Which is always nice.
You could simply paint your nails black, then dot them with white polish... or the easiest option is to cheat with some polka dot nail wraps.
Try Nail Rock Nail Wraps in Seeing Spots, £6.65, nailrock.com.
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Let us know what you think of Katy's matching dress and nails below. Our fave comment across the site each week wins £50!