Nicky's older sister, Paris Hilton, served as a bridesmaid in a soft powder blue dress, while proud parents, Richard and Kathy, were on hand. Aunt Kyle Richards was also there to see her niece walk down the aisle.
Celebrity wedding guests included supermodel Naomi Campbell, Chelsea Clinton and her husband, Marc Mezvinsky, and billionaire Formula One heiress Petra Stunt -- it was actually at Petra's 2011 wedding to James Stunt where the couple met. As for post-nuptial entertainment, the couple will be serenaded by none other than Lionel Richie.
Check out Nicky's walk down the aisle.
Prior to the big day, Nicky and James held a pre-wedding dinner on Thursday night at Spencer House in St. James's for close friends and family. Check out this super-cute snap of the couple smooching before the ceremony. "So happy that my sister found the man of her dreams," Paris Instagrammed. "They make the perfect couple! So excited for their wedding today! #MrsRothschild."
Friday's nuptials marks Nicky's second marriage. Nicky married businessman Todd Meister in Las Vegas in August 2004, but it was annulled just three months later. She's been engaged to James since August 2014, and they've been dating since 2011.