Britney took the opportunity to also celebrate their recent engagement, with Britney showing off her stunning Neil Lane sparkler for the cameras.
She even shared the moment with her fans on Twitter, writing: 'Tonight was one of the most magical nights of my life. Such an amazing time with my new fiance and our closest friends and family. #Blessed.'
Wedding belle: Britney and Jason happily posed for pics at his 40th birthday. Photo: WireImage
Earlier in the night, she also shared her plans, saying: "Still glowing! About to jump on a plane to Planet Hollywood in Vegas. Throwing a Bday Party for Jason at Chateau Night Club. So fun. Xxoo."
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Ready for its close-up: Britney's Neil Lane sparkler was twinkling. Photo: WireImage