The Princess of Wales received cheers as she walked onto court to present the trophy to Carlos Alcaraz.
The 42-year-old, wearing a purple dress, was accompanied by her nine-year-old daughter Charlotte as she talked to players before the match.
She was then cheered by onlookers as she made her way to Centre Court.
The crowd took to its feet as the princess, patron of the All England Club, entered the arena, applauding for around 30 seconds.
Catherine waved as she took her seat next to her sister Pippa in the royal box, close to actors Tom Cruise, Zendaya and Hugh Jackman.
At the end of the match, she walked onto the grass to more cheers, offering consolatory words and a silver plate to runner-up Novak Djokovic and the winner's trophy to Alcaraz.
Djokovic, a seven-time Wimbledon champion, said it was a "privilege" to be in the presence of the princess again.
"I've said to her that it is very nice to see her in good health," he said. "She seems to be in good health. That's obviously very positive news for everyone in this country."
Earlier in the tournament she sent a social media message to British great Andy Murray, writing: "An incredible #Wimbledon career comes to an end. You should be so very proud @andy_murray. On behalf of all of us, thank you! C."
Catherine tentatively returned to UK public life last month for the first time since her diagnosis, attending a military parade in London to officially mark King Charles III's birthday.
It came nearly three months after she revealed she was receiving chemotherapy treatment. She had not been seen at a public engagement since a Christmas Day service last year.
In a statement at the time, she said she was "making good progress" with her treatment, which is set to last for several more months, but was "not out of the woods yet".
The cancer announcement came just weeks after it was disclosed that British head of state Charles had also been diagnosed with the condition.
Neither has revealed what type of cancer they have.
Charles, 75, was given the green light to resume public duties in April, after doctors said they were "very encouraged" by his progress.
He has since attended commemoration events in northern France for the 80th anniversary of the D-Day landings during World War II.
Royal officials are keen to manage expectations about Kate's gradual return to the public eye, and have maintained that her appearances will depend on her treatment and recovery.
Kate said in her statement in June that she had "good days and bad days" and was "taking each day as it comes".
AFP