Kate was featured in the Court Circular after holding a meeting at Windsor Castle about an issue that aides in the past have described as her life's work - the early years development of children.
She was joined on Tuesday by her household team and staff from the Royal Foundation Centre for Early Childhood, the organisation she established to promote the issue and conduct research.
It is only the third time she has been mentioned in the official record of royal engagements since her health scare began at the start of the year.
The Court Circular stated: "The Princess of Wales, Joint Patron, the Royal Foundation of The Prince and Princess of Wales, this afternoon held an Early Years Meeting at Windsor Castle."
The meeting is likely to have discussed the princess' ambitious Shaping Us campaign, launched last year by the centre with the aim of raising the profile of the formative years of a child's life.
Kate recently announced the completion of her chemotherapy treatment in a deeply personal video with her family and said her focus was "doing what I can to stay cancer free".
Her heartfelt message about her cancer journey was spoken over images showing Prince William and their children enjoying the outdoors, walking through woods and the couple shown cuddling as they hold hands.
View this post on Instagram A post shared by The Prince and Princess of Wales (@princeandprincessofwales)
The princess had been receiving chemotherapy for an undisclosed form of cancer since late February with the King beginning his cancer care earlier that month following his diagnosis after treatment for an enlarged prostate.
While receiving treatment, Kate had been undertaking some work behind the scenes, meeting with her staff and representatives from the centre but these were not officially recorded.
She attended the King's birthday parade, also known as Trooping the Colour, in June and the following month presented the winning trophy in the men's Wimbledon final to Carlos Alcaraz, with both events featured in the Court Circular.
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