The sisters-in-law are cheering on Meghan's close friend Serena Williams as she takes on Simona Halep.
Sporting a Hugo Boss skirt and Givenchy shirtl, the Duchess of Sussex also donned a pair of Le Spec sunglasses and a Stella McCartney handbag.
Kate, meanwhile, wore a green short-sleeved Dolce and Gabbana dress which featured gold buttons.
Meghan and Williams are close friends, with Williams attending her wedding to Harry last summer.
When asked about the negative press, Williams said she never reads anything about Meghan in the news.
“She couldn’t be a better friend to me. Low moments, high moments, she’s always there,” Williams said.
“That’s all I want to be to her.”
The duo's day out comes just days after Meghan was slammed by royal fans after she instructed her royal security personnel to inform spectators at Wimbledon not to take photos of her.
Despite being a public figure, Meghan insisted that she was at the Grand Slam in a 'personal capacity' so to watch her friend Serena William play, and therefore off duty.
Having been previously dubbed 'Duchess Difficult' after rumours of her diva demands made their way from the palace and into the public, the new mum is now being mocked for her 'no photos' request, earning the nickname 'Princess Privacy'.
Meghan Markle's security stops fan from taking photos of duchess at Wimbledon
Earlier this week, Kate and Meghan were also seen spending time together at the Polo where they watched their husbands Prince William and Prince Harry take part in a charity match.
The pair were all smiles as they cheered and chatted from the sidelines with their adorable children, Master Archie Harrison, Prince George, Princess Charlotte and Prince Louis.