The 35-year-old royal pulled out all the stops for the outing, sporting a white lace mini dress by Alexander McQueen. She completed the classy look with a matching bespoke hat, dangly pearl earrings, nude clutch and suede Gianvito Rossi heels.
Her husband, Prince William, also dressed to impress, looking dapper in a top hat and tails.
Middleton spent the day hanging out with Sophie, Countess of Wessex, who looked equally chic in an emerald green dress and tan hat. Judging from the photos, it appears the two exchanged a lot of laughs throughout the day, at one point breaking out in a full-on giggle fest.
The stylish ladies had another funny moment when it was time to hop into their carriage. The Countess of Wessex lost her balance, nearly taking a tumble onto Middleton. Luckily, the mother of two was able to keep her friend stable, avoiding a public mishap.