It was a full house at Sandringham as four generations gathered for the festivities on the Norfolk estate.
Wiliam and Kate looked relaxed as they made the journey to St Mary Magdalene Church on foot holding hands. But there was no sign of Prince George as temperatures stayed just above freezing.
One member of the crowd shouted: "Where's the baby?"
Wearing a tartan Alexander McQueen coat and hat by Gina Foster, Kate smiled and waved to the crowds.
She was seen curtseying to the Queen, who was wearing an orange coat, as the family attended a private service earlier in the morning.
Prince Harry, still sporting a beard from his exertions in the Arctic with the charity Walking With the Wounded, attended alone despite rumours that his girlfriend Cressida Bonas might join him.
About 3,000 well-wishers gathered outside the church to watch them arrive.
Before the service a pilot entertained them by drawing a smiley face, heart and kiss in vapour trails in the sky.
The service opened with a rendition of Christians, Awake followed by Once In Royal David's City.
Recent years have seen reduced numbers - last year the Duke and Duchess of Cambridge chose to spend Christmas Day with Kate's family in Berkshire, while Prince Harry was on tour in Afghanistan.
In 2011, Prince Philip was absent from many public appearances after being admitted to hospital for a heart operation.
There had been unconfirmed reports that grandparents Michael and Carole Middleton would also attend. There was no sign of them but it is thought they may arrive at the estate tomorrow.
The royal habit of spending Christmas at Sandringham is believed to date to Queen Victoria's reign.
The family traditionally open their presents on Christmas Eve and will enjoy a Norfolk turkey with all the trimmings after today's service.