Middleton, 33, looked smashing in a pale pink jumpsuit with a ruffle on the top. She accessorized her ensemble with red shoes and an adorable heart-shaped clutch. Noticeably absent from her right hand was her giant engagement ring, worth a reported $323,550.
Pippa appeared to be enjoying the star-studded charity event and mingled with guests, which included Princess Eugenie, Duchess of York Sarah Ferguson, Lady Carina Fitzalan-Howard and David Furnish.
The celebration was thrown to raise money for research for hypertrophic cardiomyopathy (HCM), a heart condition which Sir David Frost's son, Miles, died from in 2013.
Kate Middleton's younger sister and her hubby returned to London this week after a month-long honeymoon. The couple tied the knot in a lavish wedding on May 20 in front of 150 guests, including Prince William, Prince Harry and sister Kate. From there, they embarked on a romantic getaway in the French Polynesia and Australia.