Her Royal Highness has organised her customary Christmas carol concert at the iconic London venue, with guests including members of the royal family, famous faces, and community champions who have made a difference in their neighbourhoods.
The large audience will listen to a selection of carols, music and readings from performers including Kate Winslet and Chiwetel Ejiofor.
The theme of the concert, held in the candle-lit Abbey on Friday, is generosity and expressing affection towards one's neighbour.
Attending the event are Jonathan and Anna Cordiner, whose child passed away from a brain cancer, and who established a foundation, Kayleigh's Wee Stars, to help households where there is a youngster facing a life-limiting condition.
"The dedication, empathy, and kindness you show, often without fanfare or recognition, and without any thought of thanks or praise, make an profound impact to the circumstances of individuals," wrote Catherine in a message before the concert.
The royal has been undertaking her own measured re-emergence to official duties after her cancer diagnosis and chemotherapy, last month delivering her first public speech for two years, in which she reflected on recognising the "discreet, frequently unseen labour of caregivers".
Those coming to the Abbey will be entertained by budding artists aided by the Future Talent charity, set up with the help of the former royal to increase availability of music lessons.
Trumpeter Carys Wood, 18, who performs on the trumpet and is from Pembrokeshire, has been supported by the organisation, with awards contributing to instruments, tuition, and transportation expenses - and she said it was "incredible" to be playing at the evening's event.
"Musical pursuits are frequently pricey," she stated. She is now studying at the prestigious music academy, 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. "It's unbelievable that I get to perform here in front of so many notable figures," she said.
Within the audience will be representatives of different generations.
That will include nine-year-old Saphia Turner, recipient of a prize for youthful altruism, who produces drawings and undertakes charity feats to generate funds for food banks.
The Abbey has been decorated with custom-created holiday decorations, with well-known chef Mary Berry and flower expert Simon Lycett assisting in their creation.
Taking to the stage will be Katie Melua, the Abbey's own choir and a nautical singing ensemble, the group Fisherman's Friends, who said the chance to take part was "the icing on the cake for us."
The festive event titled 'Together at Christmas' will be televised and shown on a major network on Christmas Eve.