The Princess of Wales is hosting her customary Yuletide celebration at the iconic London venue, with guests including dignitaries, stars, and everyday helpers who have helped their communities.
The 1,600 guests will listen to a blend of festive songs, musical performances, and spoken word pieces from actors such as award-winning actors.
The central message of the event, held in the candle-lit Abbey on the afternoon, is kindness and showing love to others.
Attending the event are a couple named the Cordiners, whose young girl was lost to a tumour, and who established a foundation, Kayleigh's Wee Stars, to support families who have a youngster facing a life-limiting condition.
"The dedication, empathy, and kindness you show, often quietly and unspoken, and without any hope for reward or acknowledgement, make an extraordinary difference to the lives of others," the Princess expressed in a note prior to the carol service.
The princess has been making her own steady comeback to public life following her health challenges and treatment, in November making her major oration since 2023, in which she talked about recognising the "discreet, frequently unseen labour of caregivers".
Those coming to the Abbey can listen to budding artists backed by the Future Talent organisation, co-founded by the former royal to widen access to instrumental training.
An 18-year-old named Carys Wood, who performs on the trumpet and is from southwest Wales, has been helped by the charity, with grants helping towards musical instruments, lessons and travel costs - and she said it was "amazing" to be performing at the evening's event.
"Musical pursuits are frequently pricey," Carys said. She is now enrolled at the renowned conservatoire, and added that "each individual ought to be given the possibility" to hone their artistic talents.
Her younger sibling Eliza, aged 11, who is a euphonium player, will be present at the Abbey. "I never thought I'd be able to play there in front of so many notable figures," she said.
Within the audience will be representatives of different generations.
That will feature nine-year-old Saphia Turner, winner of a prize for youthful altruism, who sells artwork and carries out sponsored challenges to raise money for local food charities.
The Abbey has been adorned with custom-created holiday decorations, with well-known chef Mary Berry and flower expert Simon Lycett assisting in their creation.
The musical lineup includes Katie Melua, the Abbey's own choir and a maritime folk band from Cornwall, Fisherman's Friends, who said the opportunity to perform was "the icing on the cake for us."
This annual carol service will be broadcast on ITV1 on Christmas Eve.