For the occasion, the Duchess of Cambridge chose a beautiful red coat dress.
For jewellery, the Duchess donned her sapphire engagement ring and matching dangling earrings.
She also accessorised the look with her £640 Miu Miu bag.
She wore her brunette hair down and was seen carrying a black face mask.
The mother-of-three was all smiles as she chatted to other guests at the Christmas carol service.
The Together At Christmas event in London is celebrated to honour the pandemic heroes such as charity workers, teachers and other volunteers.
The Duke and Duchess of Cambridge were joined by Sophie, Countess of Wessex.
Sophie donned white trousers and a green blouse which she combined with a maroon jacket.
The service included performances from stars Ellie Goulding and Leona Lewis.