The Scottish actor became involved with It's Good 2 Give after the charity helped a 16-year-old girl, whom Capaldi has met and supported through her battle with a rare form of cancer.
He is backing the group's latest campaign, which aims to build a luxury residential home in Callander, Scotland that families of cancer sufferers can use when they need a break.
In a statement, the star says, "I was introduced to It's Good 2 Give after the charity had helped a family I know. I was hugely impressed by their approach and ambition. By spreading the word I hope to help them raise the funds they need. It really is Good 2 Give; please help them by giving what you can."
It's Good 2 Give's founder, Lynne MCNicoll, adds, "You can't imagine how excited we are to have the support of Peter. We are at a critical stage in our fundraising and desperately need to reach out to people who are keen to support everyday families who are battling with the emotional and physical challenges of caring for a child who is seriously ill."