The Duchess hosted the event as a way to shine a light on those who have gone the extra mile this year to help people in need.
She shared animated conversations with several people, including young Mila Sneddon, who actually met Kate earlier this year. The six-year-old suffers from leukaemia and featured in the royal's Hold Still photography project which launched in February.
Ever so sweetly, the young girl was ecstatic to meet the Princess at the time and was just as excited at the carol service—she even gave her another twirl.
Joining Kate for the remarkable event were a bunch of familiar royal faces.
Kate's mother and father, Carol and Michael Middleton, arrived with her two siblings James and Pippa Middleton. James also brought along his wife, Alizee Thevenet, whom he married in September this year.
Also joining the Middletons were members of the British royal family, including Sophie of Wessex, Princess Beatrice and her husband Edoardo Mapelli Mozzi, Princess Eugenie, as well as Zara and Mike Tindall.
The latter three royals have all welcomed children this year, undoubtedly something that's brought them closer together.
The service, named Royal Carols: Together at Christmas, was broadcast across the UK. Kate and William released a statement shortly before the service commenced to remind viewers of the real reason for the celebration.
"We will be reflecting on the extraordinary challenges we have faced in recent times and celebrating the acts of kindness that we have witnessed across the nation as communities pulled together to help each other and protect those in need."
