The service, which took place at the Cenotaph in Whitehall, London, marked Princess Kate's third official royal engagement since finishing cancer treatment.
She wore her glossy chestnut tresses in a chignon, and accessorised with a netted button hat and diamond and pearl drop earrings which previously belonged to the late Queen.
In a nod to her role as the regiment's Colonel-in-Chief, Kate completed her look with her silver Queen's Dragoon Guards brooch.
Echoing Kate's outfit, Sophie opted to wear a sophisticated black dress complete with a cowl neckline. She elevated her ensemble with a wide-brim hat, a string of pearls and sparkling earrings.
Prince William donned his Royal Air Force uniform while King Charles looked smart in his Royal Navy uniform of the Admiral of the Fleet.
As a mark of respect, the royals all wore red poppies to acknowledge those who died during conflict. The late Queen Elizabeth II used to wear five poppies and it is thought that they represented each service in the war: the Army, the Navy, the RAF, the Civil Defence and women.
When the bells of Big Ben tolled eleven, a single gun on Horse Guards Parade was fired and two minutes of complete silence was held in remembrance of all lost in war.
After a further round of gunfire signifying the end of the silence, the bugle call 'The Last Post' was played.
WATCH: The royal family are seen in silence at the Remembrance day service
During the service, the monarch, who is Head of the British Armed Forces, laid the first wreath at the Cenotaph.
His wreath closely resembled a floral tribute produced for his grandfather King George VI – 41 open-style poppy petals made from bonded fabric mounted on black leaves, traditional for a sovereign's wreath and featuring a tied ribbon in the colours of the King’s racing silk – scarlet, purple and gold.
Major Ollie Plunket laid a wreath on behalf of Her Majesty. Queen Camilla's wreath resembled the wreath produced for HM Queen Elizabeth The Queen Mother.
It featured 95 closed style poppy petals made from bonded fabric and ribbon using the colours from the Queen's racing silk - brown, red and yellow.
Prince William also laid a wreath during the service.
Also in attendance at the national memorial service were Princess Anne, the Duke of Edinburgh, the Duke of Kent as well as politicians, the armed forces and some 10,000 veterans.
British former Prime Ministers Rishi Sunak, Liz Truss, Boris Johnson, Theresa May, David Cameron, Gordon Brown, Tony Blair and John Major also attended the annual Service Of Remembrance.
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Following the service, members of the royal family departed from the Cenotaph and entered the Foreign, Commonwealth and Development Office.
Queen Camilla was not present due to her ongoing chest infection. A statement shared on Saturday read: "Following doctors' guidance to ensure a full recovery from a seasonal chest infection, and to protect others from any potential risk, Her Majesty will not attend this weekend's Remembrance events.
Queen Camilla is recovering from a chest infection
"While this is a source of great disappointment to The Queen, she will mark the occasion privately at home and hopes to return to public duties early next week."
On Saturday, Kate also attended the Royal British Legion Festival of Remembrance. The annual event, which takes place on the eve of Remembrance Day, is an opportunity for the nation to pay respect to those who served, and to those who sacrificed their lives during World War I.
Kate wore an elegant black coat dress and a pair of Jimmy Choo pumps
Princess Kate's consecutive outings come after Prince William shared a rare update regarding his wife's health. Whilst in Cape Town for the Earthshot Prize Awards, William told broadcasters: "She's doing really well thanks. And hopefully she is watching tonight. So cheering me on. She's been amazing this whole year. I know she will be really keen to see tonight be a success."
Back in September, Kate shared her "relief" as she confirmed she had completed the course of preventative chemotherapy in an intimate and moving video message.
In a personal update Kate, 42, opened up about her experience, saying it has been "incredibly tough" for her family and they "have had to find a way to navigate the stormy waters and road unknown".
The Princess continued: "Doing what I can to stay cancer free is now my focus. Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes.
"I am however looking forward to being back at work and undertaking a few more public engagements in the coming months when I can."
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