The Duke of Cambridge is seen kissing his youngest child Prince Louis in a new photograph taken by his wife.
The black-and-white picture was taken by the Duchess of Cambridge in Norfolk earlier this year and released on Christmas Day.
It also shows Princess Charlotte and Prince George, who are due to attend the Sandringham Christmas Day church service for the first time later.
The picture was posted on social media with the message: "Merry Christmas".
In the photo, the duke wears a flat cap as he holds his youngest son, with Princess Charlotte standing beside them.
Prince George sits next to them in a chair as he smiles at the camera.
The duchess has previously been praised for her photographic portraits of her children and was named as the new patron of the Royal Photographic Society earlier this year.
Kensington Palace has often published photos taken by Kate to mark milestones in her children's lives, such as birthdays and first days at nursery.
The duchess began the tradition in 2015 when she took the first official portraits of Princess Charlotte, rather than hiring a photographer.
Members of the Royal Family will attend a Christmas Day church service in Sandringham, Norfolk, later.
It comes after the Duke of Edinburgh returned to the Queen's estate following a four-night stay at a hospital in London.