The duchess was all smiles as she met youngsters receiving care in the south London hospital and their parents.
Beaming Kate has been named patron of the children's hospital ahead of her visit, and made sure to demonstrate how thankful she was for the honour by spending time with the little patients and taking part in Christmas themed activities.
In her new role of official figurehead of the hospital, Kate will have the opportunity to champion medical professionals working on the front line in children's healthcare, and shine a light on their work supporting youngsters in their early years.
For the occasion, Kate chose to wear a classy mid-length polkadot dress from L.K Bennett, which perfectly framed her figure with a bow at the collar and elegant pleats in the skirt.
The stylish duchess teamed the £325 dress with a suede pair of £195 khaki court heels and a matching £175 clutch bag.
And a relaxed Prince William wore a dark suit with a pale blue shirt
The hospital, which provides comprehensive health services to children and families from before birth, throughout childhood and into adult life together with specialist services for youngsters with rare and complex conditions, is getting ready to celebrate its 150th anniversary in 2019. Read more from EXPRESS.