As keen tennis fans, they looked thrilled as Andy Murray began his quest for glory, looking to enter history as the first Briton to win Wimbledon in 74 years.
But excitement soon turned to trepidation for the Duchess of Cambridge and her sister Pippa Middleton during the Scotsman's nail-biting four-set match with Roger Federer.
The sporty siblings were enthralled by the action, displaying a range of emotions as Andy valiantly battled his Swiss opponent, known as the champion of champions.
Sitting in the royal box, Kate was seen tensely clasping her hands and 'ooo-ing' and 'aahh-ing' as the match swung towards Roger.
Both sisters applauded when he prevailed, winning his seventh title at the All England Club, but disappointment was visible on their faces.
Kate was seen biting her bottom lip, trying to keep her emotions in check, when the 25-year-old Scotsman broke down during the traditional post-match interview.
He eventually gathered himself enough to joke: "I am getting closer".
Then the player thanked his support team including his parents and girlfriend Kim Sears, who was also in tears, before paying tribute to the crowd.
"They make it so much easier to play. The support has been incredible," said Andy.
His royal supporter Kate looked elegant in a cream Joseph tweed jacket, which debuted she wore for last year's Epsom Derby, and a crepe shift dress which she bought for her North American tour with Prince William last year.
Pippa opted for a £350 Phoebe frock – decorated with bluebird motifs – from Dannii Minogue's Project D range.
Also watching were Kate and Pippa's parents Carole and Michael – whose seats came courtesy of Tim Henman's parents Jane and Tony Henman.
William had been invited to attend the final, but instead he went surfing with his brother Prince Harry in Cornwall.
Interviewed after the match, champion Roger, who was cheered on by his two-year-old twin girls Myla Rose and Charlene Riva and his wife Mirka, said: "[Andy] has done so well over the years and it [his tears] shows he cares so dearly about his tennis.
"He will win one grand slam at least. I hope so. It's worked out here that I have played my best tennis in the semis and the final.
"I couldn't be more happy. It feels so familiar and it's a great moment. It's amazing."