Royal baby Archie had his grandfather smiling when the Prince of Wales was congratulated by well-wishers on the birth.
Charles was happy to chat about his grandson when he stopped to greet a group of tourists during his visit to a centuries-old monastic site in Ireland's Wicklow mountains.
The Duchess of Cornwall described the Duke and Duchess of Sussex's son as "still very little" during a visit to the Republic's oldest working mill in Avoca Village.
Heir to the throne Charles, making his fifth visit to Ireland in as many years, visited Meghan and Harry's baby son with Camilla soon after they returned from a tour of Germany.
Charles stopped to speak to a group of American and Australian tourists who called out to him as he visited the Glendalough Monastic Site.
"Congratulations on the birth of your new baby grandson," said a woman who was visiting from Australia.
"Oh, you're very kind," a smiling Charles replied.
Camilla spoke about Harry and Meghan's baby when she met well-wisher Jo Wallace, who handed the duchess a bouquet of flowers at the mill.
Ms Wallace, who was with her own grandchildren, said "congratulations on your grandchild, the new one", as the pair shook hands.
The duchess replied: "Yes, the new one indeed, he's still very little."
Charles met a group of local children who were cataloguing moths caught overnight on the shores of the picturesque area's Upper Lake.
Aaron Conway (12) said: "He was saying about how he likes the environment and that it was really fascinating all the different moths we were identifying."
The prince was also taken with a mountain rescue dog called Rowan, a three-year-old collie cross, who was with his handler Sheelagh O'Malley from Glen of Imaal Wicklow Mountain Rescue.
She said: "He seemed more interested in the dog, he's a real dog person - but he is a very cute dog, I have to say. He's got a massive work ethic. When I put on his mountain rescue jacket he knows it's time for work and when I take it off he relaxes."
Before leaving the area, Charles went on a brief walkabout and was surrounded by walkers who had gathered nearby when they realised he was visiting.