Kate, 40, led the charge as she arrived at the storied royal church solo to greet fans and get ready for her performance this evening.
The Duchess of Cambridge and Cornwall was all smiles as she waved for the cameras, before walking into London’s Westminster Abbey.
She later returned to the walkway to collect her husband, Prince William, and their two eldest children, Prince George and Princess Charlotte, and re-enter the abbey. Their youngest child, Prince Louis, appears to have stayed at home.
The Cambridge family then walked up to the steps of Westminster Abbey with King Charles and his wife Queen Camilla, as the entire Royal Family put on a united front following the release of the final three episodes of Prince Harry and Meghan Markle's bombshell Netflix documentary.
Kate wore a monochrome look in a festive burgundy shade for the symbolic event, wearing a coat dress in her signature A-line shape, and accessorising with matching gloves, shoes and clutch bag.
Her hair was styled in its signature loose waves, and ruby drop earrings caught the shimmer of Christmas lights.
Although Kate led the way for the Royal Family, other senior working royals weren’t far behind.
Sophie, Countess of Wessex was one of the first to arrive, in a chic cream coat, matching cream polo-neck knitted jumper and knee-high brown leather boots.
Soon, the royal cousins arrived in abundance: Princess Beatrice, and her husband Edoardo Mapelli Mozzi, Princess Eugenie with husband Jack Brooksbank, and Mike Tindall, fresh from the I’m A Celebrity jungle.
Zara Tindall arrived a few moments later with Kate's family, including her sister Pippa and mother Carole, followed by His Majesty the King and with his wife, Queen Camilla.
Presided over by The Princess of Wales, and supported by The Royal Foundation, the service will “recognise the selfless efforts of individuals, families and communities across the UK”, and celebrate and “showcase the joy that human connection and togetherness can bring”.
Although the mother of three was at the forefront of the event in 2021, this year will be particularly poignant as it is the first Christmas since the death of Queen Elizabeth, and Kate’s first event of this scale as a spearhead since becoming the Princess of Wales.
The service will pay tribute to the late Queen and “the values Her Majesty demonstrated throughout her life, including duty, empathy, faith, service, kindness, compassion and support for others.”
Last year, as well as hosting, Kate joined in with performing, too, turning her hand to playing the piano accompaniment for singer Tom Walker, for his rendition of For Those That Can't Be Here.
This year's carol service will combine "traditional and modern elements to encompass people of all faiths," as King Charles is plans to become a "monarch of all faiths" and will be televised in a special broadcast this Saturday.
The world-renowned Westminster Abbey choir will perform some of the nation’s most beloved carols, including ‘O Come, All Ye Faithful’, which was selected through a public poll last week, and readings are set to be delivered by speakers including The Prince of Wales, Dame Kristin Scott Thomas, Hugh Bonneville and Kadeena Cox.
Royal Carols: Together At Christmas will be broadcast Christmas Eve at 7pm on ITV.
Watch: Kate hosts star-studded carol service at Westminster Abbey