Prince William personally delivered his son's letter to Santa while in Finland.
Kensington Palace posted a photo of Prince William delivering the letter as he visited the Christmas Markets in Esplanade Park.
The prince was also captured greeting children holding miniature British flags.
"The Duke of Cambridge meets Father Christmas in Esplanade Park in Helskini," the palace wrote.
"The Duke then handed over a letter written from Prince George to Father Christmas #RoyalVisitFinland #Finland100."
Prince George said in the letter that he had been "nice" and asked for a toy police car, according to People. The young royal left the remaining four spots on his list blank.
"I've seen you and I had to give you this letter," Prince William said. "He hasn't written down many requests, so I think one request is probably OK."
Prince William had reacted to brother Prince Harry's engagement to Meghan Markle after arriving in Finland on Wednesday. He told reporters he and wife Kate Middleton are "very excited" for the couple to wed.
"We're very excited and delighted for them both and wishing them all the happiness in this very exciting time," the prince said.