The Prince of Wales spoke of his shock after hearing that a child as young as four had contemplated taking her own life.
William and Kate were told of the growing number of young people receiving support from suicide and self-harm prevention counsellors as they visited a charity in Belfast.
PIPS, which was founded in 2003, offers help to young and old dealing with mental health issues across Northern Ireland.
The prince and princess were told that the youngest person it has helped deal with suicidal thoughts was a four-year-old girl while the oldest was a 92-year-old man.
William expressed surprise when he heard that someone so young had thought about ending their life.
“To have that awareness at four years old to do that is really quite shocking,” he said.
The princess hailed the worked of the charity as inspirational as she talked with volunteer counsellors.
“You’re very inspiring,” she said.
During their visit, William and Kate took part in an art therapy session, painting pumpkins, with some vulnerable children who have been supported by PIPS.
They also joined a group of volunteer counsellors in packing up the charity’s Little Boxes Of Hope.
The support packages are given to children following their time with PIPS to assist their ongoing recovery.
The royal couple also spent some time speaking with 24-year-old Erin Quinn, who has sought support from PIPS in the past.
Afterwards Ms Quinn hailed the prince and princess’s approach.
“My experience today was that people actually do listen,” she said.
“I was completely shocked because I didn’t know that William and Kate were coming here but all my nerves kind of subsided when they came in because they just seemed to be quite normal people.
“And they had a genuine interest in mental health and what PIPS is, what does PIPS do, how does it help people.
“I did share with them a little bit of my past experience in mental health and ongoing mental health issues and I just felt they were really engaged, they asked me questions, they wanted to really see inside and what was going on.”
Executive director of the charity Renee Quinn (no relation to Erin Quinn) said the visit meant so much to the charity.
“Today was a fabulous visit, we are absolutely honoured and delighted that the Prince and Princess of Wales were able to visit our charity, we’re very humbled to have them visit our charity,” she said.
Renee Quinn said the prince and princess had been concerned to hear at the growing need for support services for younger people.
“That was very alarming to them,” she said.
“Unfortunately, it’s a trend that we have seen, particularly throughout Covid.
“We always did deal with children clients, but unfortunately we are seeing a lot younger coming through our doors, so much so that we have now got a child and youth counsellor service specifically to deal with the children.
“So, they were fascinated to learn about that service.”