It was her first outing after being forced to self-isolate when she came into contact with a person with Covid-19.
The duchess, in an emerald green dress, was accompanied by her husband Prince William to watch the match between Ash Barty and Karolina Pliskova from the Royal Box.
Keen tennis fan Kate presented the trophies to winner Barty and Czech finalist Pliskova.
A tweet from the royal couple’s official account, read: “What an incredible match and performance by both athletes! Congratulations @ashbarty on being crowned #Wimbledon champion.”
William donned a light blue suit jacket, light-coloured shirt, dark trousers and tie, with the couple both wearing face masks.
Also in the crowd for the game was Hollywood star Tom Cruise who was with actress Hayley Atwell.
It is the first time since 1977 – the year Virginia Wade won the title – that two first-time finalists have met in the women’s showpiece.
The roof stayed open on Centre Court despite the unsettled weather while the royal couple enjoyed a chat with former Wimbledon champion Billie Jean King who sat behind them.
Just a few rows behind the couple in the Royal Box sat actor Priyanka Chopra, who is known to be a friend of their sister-in-law, the Duchess of Sussex.
It is the start of a bumper weekend of sport with the Men’s singles final tomorrow as well as England’s clash with Italy at Wembley for the final of Euro 2020.
The duchess will also attend the men’s game, though without her husband, after completing a period of self-isolation.
Kensington Palace said her self-isolation period had finished by Saturday but did not confirm when it officially ended.
The duchess began self-isolating on July 2 after being alerted that afternoon that she had come into contact with someone who later tested positive, but it is not known if the NHS app made her aware.
She had visited Wimbledon that day and had toured the SW19 tennis club, met staff at the venue and watched Britain’s Jamie Murray compete in a doubles match.
Kate is a keen tennis fan and patron of the All England Lawn Tennis Club, and she has regularly attended the Wimbledon championships since her marriage to William in 2011.
She joined William with their son Prince George at Wembley to watch England’s Euro 2020 victory over Germany last week.
William and Kate follow a royal testing regime for coronavirus, taking two lateral flow tests a week with additional testing before public engagements such as sporting events.