Having been one of the lucky few invited to all parts of Harry and Meghan's wedding last month, the 36-year-old tennis icon was all smiles as she relaxed and enjoyed some quality girl time with her friend.
With the temperature at Cowarth Park Polo Club in Berkshire nearing 30C, Meghan wore an appropriately cool summer dress.
She paired the stylish dress with a pair of Grear leather sandals from Sarah Flint NY, some dark tinted sunnies and a white and black Madewell x Biltmore panama hat.
Prince Harry was competing in the match for the second day after making a surprise appearance on Friday.
There's also the royal train - which the Queen and Meghan Markle used just weeks ago to visit Cheshire - which reportedly costs around £20,000 per trip.
Serena is now in England while she prepares for the Wimbledon tennis tournament, which kicks off in just a couple days.
Kate Middleton was not in attendance, however Williams made headlines yesterday when she labelled the Duchess one of her all-time "bad ass" women in an interview with InStyle magazine. Serena had withdrawn in the fourth round from the French Open due to a strained muscle after giving birth to her daughter less than a year ago.
She gave birth to her first baby, daughter Alexis Olympia Ohanian Jr, on September 1, 2017.
Guest Serena Williams has been waging a campaign for new mothers to retain their seeding status at Wimbledon after taking time off for motherhood.