Catherine arrived for the Festival of Remembrance at the Royal Albert Hall on Saturday wearing a black dress adorned with a red poppy, which has become a symbol of respect for those who have lost their lives in conflict.
She was accompanied by her husband and heir to the British throne, Prince William, and other members of the royal family including Anne, the Princess Royal, and was followed shortly afterwards by King Charles III, whose wife Queen Camilla has cancelled engagements as she recovers from a chest infection.
The 42-year-old said in September she had finished chemotherapy, but her path to full recovery would be long. At the time, she said she would be carrying out a handful of public engagements later in the year.
Catherine and William have three children.
In October, she met the bereaved families of three young girls who were murdered at a dance class in northwest England.
Catherine is also expected to attend the main Remembrance Day ceremony on Sunday, Buckingham Palace said.
The ceremony at the Cenotaph war memorial is held on the nearest Sunday to November 11 to mark the end of World War 1, and pays tribute to those who lost their lives in war.
Camilla hopes to return to public duties early next week, the palace said.
She pulled out of planned engagements this week after her doctors advised a period of rest and would mark Remembrance Day privately at home.
In South Africa, William told British media on Thursday that the past year had probably been the "hardest" of his life after Catherine and the King were diagnosed with cancer.
The Prince of Wales visited South Africa as part a climate-focused trip planned around his multimillion dollar Earthshot Prize, created to encourage innovations to combat environmental problems.
As he prepared to leave South Africa, William said, in remarks published on Saturday by British media, he was trying to carry out his public duties "differently" from previous generations.
"I'm doing it with maybe a smaller R in the royal. It's more about impact philanthropy, collaboration, convening, and helping people.
"And I'm also going to throw empathy in there as well, because I really care about what I do. ... I think we could do with some more empathetic leadership around the world."
