The Princess of Wales is hosting her yearly festive musical service at the iconic London venue, with guests including dignitaries, stars, and everyday helpers who have supported their local areas.
The 1,600 guests will listen to a blend of festive songs, musical performances, and spoken word pieces from stars like Chiwetel Ejiofor and Kate Winslet.
The theme of the event, held in the candle-lit Abbey on the afternoon, is compassion and demonstrating care for others.
Attending the event are Anna and Jonathan Cordiner, whose child passed away from a brain tumour, and who established a foundation, a charity called Kayleigh's Wee Stars, to support families who have a terminally ill child.
"Your efforts, love, and understanding, often without fanfare or recognition, and without any thought of thanks or praise, make an profound impact to the lives of others," the Princess expressed in a letter ahead of the carol service.
The royal has been undertaking her own steady comeback to the public eye following her health challenges and treatment, recently giving her first public speech for two years, in which she talked about recognising the "selfless, commonly overlooked efforts of carers".
Those coming to the Abbey will be entertained by young musicians backed by the charitable trust Future Talent, co-founded by the former royal to increase availability of music lessons.
Carys Wood, aged 18, who plays the trumpet and is from southwest Wales, has been supported by the charity, with funding assisting with musical instruments, lessons and travel costs - and she said it was "awesome" to be taking part in the concert.
"Pursuing music is often costly," the musician remarked. She is now enrolled at the renowned conservatoire, and added that "each individual ought to be given the possibility" to hone their artistic talents.
Eliza, Carys's sister who is 11, who performs on the brass instrument, 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.
Among the guests will be people from various age groups.
That will feature young Saphia Turner, nine, winner of a prize for youthful altruism, who creates and sells art and completes fundraising tasks to generate funds for food banks.
The Abbey has been festooned with specially made wreaths, with well-known chef Mary Berry and flower expert Simon Lycett contributing to their design.
Taking to the stage will be Katie Melua, choristers from Westminster Abbey and a Cornish sea shanty group, the group Fisherman's Friends, who said the opportunity to perform was "a dream come true."
The festive event titled 'Together at Christmas' will be aired by ITV1 on Christmas Eve.
A certified nutritionist and wellness coach with over a decade of experience in holistic health practices.