Before today’s matches began, Kate met some of the people behind the scenes of Wimbledon, including officials, service personnel and ball boys and girls, the palace said in a statement.
Kate, wearing a bright yellow Roksanda Ilincic dress, also met the Williams sisters' mother, Oracene Price. She later watched Wimbledon's wheelchair competition as well.
Kate, 34, is a huge tennis fan and player herself. She told British player Greg Rusedski at Wimbledon today that her oldest child, Prince George, who will turn 3 later this month, has already picked up a tennis racket.
“She talked about George, her little boy, playing tennis,” Rusedski told the UK Press Association after meeting Kate. "He's got a racket and he enjoys playing tennis, and obviously she plays with William … so they obviously enjoy the sport very much."
Kate and William, who have a tennis court at their country home, Anmer Hall, in Norfolk, enjoy a fierce rivalry on the court.
Kate is reportedly the better player but admitted to Novak Djokovic after watching him in the 2014 Wimbledon men's final that the pair are pretty "even." She also told the three-time Wimbledon champion she was a bit out of practice at the time since becoming a new mother to Prince George.
Today is not the first time Kate has made an appearance in the royal box at Wimbledon. She and Prince William are often seen courtside at the All England Club and she's also accompanied her family, including sister Pippa, to enjoy the grass court play.
The princess accepted honorary membership at the All England Lawn Tennis and Croquet Club in 2013 and is expected at some point to take over from Queen Elizabeth II as honorary patron of the club, which hosts Wimbledon. William, Kate and Prince Harry have taken over several high-profile charitable patronages from Queen Elizabeth since she's turned 90.
It's possible that William and Kate may make a second appearance at Wimbledon over the weekend to support British favorite Andy Murray as he hopes to gain a spot in the men's final. The Duke of Kent, who is president of Wimbledon, currently hands out the trophies at the finals' conclusion.