The 24-year-old 'Man Down' singer wore a strapless black gown with thigh-high split, suspenders and a pair of pearl sunglasses. She later slipped into a sheer pink lace negligee teamed with a pair of pink suede ankle boots.
While performing songs 'Diamonds' and 'Fresh Off The Runway', Rihanna mingled with the lingerie label's Angels, such as Doutzen Kroes and Barbara Fialho.
Meanwhile, Bieber donned a silver vest, white leather trousers and sliver finger-less gloves, and told reporters prior to the show: "It's like a dream come true.
"I would rather be here than anywhere in the world."
Bruno Mars also performed and avoided being distracted despite being surrounded by underwear-clad models including Miranda Kerr and Lily Aldridge, who recently married and welcomed her first child with Kings of Leon frontman Caleb Followill.
Other guests gracing the pink carpet included Vanessa Hudgens, Debbie Harry and 30 Rock's Kristina Bowden.