Kate Middleton, 35, walked alongside husband Prince William, 35, and newly engaged Meghan Markle, 36, and Prince Harry, 33.
The Duchess of Cambridge wore a festive red and green check coat for the service, which she matched with a black hat.
The coat came just above her knee, and was loose enough not to show any of her baby bump.
Trimmed with gold buttons, the coat also featured a black collar.
Her legs were kept covered with thick black tights, and Kate finished the look off with black velvet block heel shoes.
She carried a matching black clutch bag and a pair of gloves in to the church too.
A pair of gold round drop earrings could be seen dangling from her ears.
The Duchess beamed as she headed into the church with her husband, but without her two children Prince George, 4, and Princess Charlotte, 2.
She was joined by Meghan Markle and Prince Harry, and the four walked along next to each other, led by Prince Philip.
Meghan wore a sleek camel coat and brown hat for the trip to church today.
Kate has been making more and more regular appearances recently, after being stuck at home with morning sickness.
She was last seen out at a memorial serivice for the victims of Grenfell Tower alongside Prince Harry and Prince William.
After church, the royals will return to Sandringham for Christmas Dinner with the Queen.
As with everything in royal life, the festive season follows a particular rhythm, and the day will go to strict timings.
The Queen’s former personal chef Darren McGrady has revealed exactly what the family enjoy.
Speaking to GoodHousekeeping.com, he said: “After church, that’s when they have a big lunch that includes a salad with shrimp or lobster, and a roasted turkey, and all of your traditional side dishes like parsnips, carrots, Brussels sprouts and Christmas pudding with brandy butter for dessert. They stick with the same meal year after year.”