The Duke and Duchess of Cambridge were given a loud ovation as they took their seats in the Royal Box ahead of six-time champion Roger Federer's match against Mikhail Youzhny.
British hope Andy Murray was set to play David Ferrer of Spain in the second match on Centre Court.
The duchess wore a white cable-knit dress with dark trim.
Last week, Prince Charles, the heir to the British throne, made his first visit to Wimbledon since 1970. Kate's sister Pippa Middleton has also been to the All England Club during this tournament.
William and Kate also watched Murray play at Wimbledon last year.