The photo comes a few days after the Duke and Duchess, Prince William and Kate, shared photographs from Louis' christening, including a candid moment of their youngest child laughing in his mother's arms.
For his christening, which took place at the Chapel Royal at St. James' Palace, Louis, who was born on April 23, was dressed in a cream christening gown which is a replica of the robe made for Queen Victoria's eldest daughter in 1841.
Queen Elizabeth II and the Duke of Edinburgh, Prince Philip, were not in attendance, with the decision understood to not have been taken on health grounds, but to have been agreed upon some time ago.
The Duke and Duchess of Sussex, Prince Harry and Meghan, were among the guests at the ceremony, marking Meghan's first royal christening. Neither will serve as godparents to Louis, with six of William and Kate's friends and other family members being chosen instead.