The 29-year-old mother of two looked in stunning shape as she relaxed with friends in a tiny multi-coloured two-piece.
The reality TV star-turned fashion designer has apparently been whipping her body into shape with celebrity fitness trainer Tracy Anderson - and the results certainly show.
Hot mama: Nicole Richie showed off her incredibly toned body in a sparkly bikini as she sunned herself in Miami yesterday
The pregnancy speculation started earlier this month, when the former Single Life star was seen leaving a gym near her Los Angeles home with something looking suspiciously like a baby bump under her work out T-shirt.
However, she slammed the idea that she was expecting a third child with rocker husband Joel Madden, 32, and said it was simply a change in her body shape.
Yummy mummy: The mother-of-two is in the Florida city for the launch of a new line from her Winter Kate fashion range
No adjustment needed: Nicole's bikini body looked just about perfect
She told celebrity website Gossip Cop: 'Contrary to recent speculation I am not pregnant. This irresponsible reporting continues to feed an atmosphere of self-doubt and insecurity.
'To publicly point out a change in anyone's body is mean-spirited and cruel. People's bodies change and change again.'
Madden and Richie already have two children together, three-year-old daughter Harlow and one-year-old son Sparrow.
Just chillin': The star was taking the chance to catch up on some R&R with friends in between her work engagements
Blonde ambition: It looked as if the reality TV star turned fashion designer had covered up her bikini in one of her own designs
The slender blonde is currently sunning herself in Miami on something of a working holiday.
Last night, the city's Ocean Drive magazine threw a party at the Neiman Marcus store in the Coral Gables area of the city to launch her latest collection from her Winter Kate range.
Nicole is certainly enjoying herself in the Sunshine State city, writing on her official Twitter account: 'Come on shake ya body baby do the Conga! #MIAMI#'
Nicole and Joel, who is also a UNICEF goodwill ambassador, wed in December last year.
When not looking after their two children when Nicole is on business trips, he's in punk band Good Charlotte.
Business woman: Nicole hosts a show to launch her latest Winter Kate collection last night at the Neiman Marcus store in Coral Gables, Miami