The Duke and Duchess of Cambridge looked relaxed as they walked St Mary Magdalene Church, holding hands 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 girlfriend Cressida Bonas might join him.
About 3000 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.
Last year the Duke and Duchess of Cambridge missed the service, choosing to spend Christmas Day with Kate’s family in Berkshire, while Prince Harry was on tour in Afghanistan.
There had been unconfirmed reports that George’s grandparents Michael and Carole Middleton would attend this year. There was no sign of them but it is thought they may arrive at the estate on Boxing Day.
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 the service.