The couple visited Southport, northwest England, "to show support to the community and hear how local people have come together as the town recovers" from a July knife attack that killed three children, the palace said.
Catherine, also known as Kate, and William met members of the emergency services who responded to the stabbing spree at a Taylor Swift-themed summer dance class, which also injured eight other children and two adults.
The couple, both 42, heard "about their experiences of responding to the attack and the impact it has had on their mental health," their office said in a statement.
The royals also met mental health practitioners who have been supporting emergency responders since the attack.
Kate announced on September 9 that she had finished her chemotherapy treatment and was striving to be cancer-free.
In a highly emotional video message following her shock diagnosis that saw her stay out of the public eye, she said she was on a long road to "full recovery".
A week later, she took a first step towards returning to her work on the early-years development of children, holding a meeting with staff from the Royal Foundation Centre for Early Childhood which she established.
It was seen as a further positive sign that Kate, a future queen, was making good progress in her cancer battle.
Footage of Thursday's engagement showed Kate, wearing a long brown coat and heels, arriving at a community centre in Southport after meeting the attack victims' families in private.
She and William spent around half an hour with each of the three family groups and were 45 minutes late arriving at the centre, according to Britain's domestic Press Association news agency.
William could be heard apologising to the waiting guests on arrival, it said.
Unrest and riots erupted in more than a dozen English towns and cities in the week that followed the events in Southport, with authorities blaming misinformation over the identity of the alleged attacker.
Axel Rudakubana, who was aged 17 at the time, has been charged with murder and attempted murder over the stabbing spree.
He is due in court later this month for a hearing.
