Kate, 32, wore the same summery dress by Zimmermann last seen on the beach in Australia in April, as she and William, 32, in a suit and tie, headed to the grand slam event to watch Brit favorite and reigning champion Andy Murray.
Princess Beatrice and her boyfriend Dave Clark were also in the crowd.
The royal presence, however, didn't bring any luck to fellow Brit Murray, who lost in straight sets to Grigor Dimitrov.
Kate, who grew up playing tennis often against her father, is a passionate fan of the game. The couple played each other at St. Andrews University when they first met and still play together today – they even have a court at their country home Anmer Hall.
Her parents, Mike and Carole Middleton, and siblings, Pippa and James Middleton, also attended matches during Wimbledon's earlier rounds.
Jonathan Hordle / REX USA