This time around, the royal attended the inaugural Global Ministerial Mental Health Summit with Prince William wearing a frock she wore on last year's goodwill tour of Poland and Germany.
Kate and Will chose a mental health summit as their first royal engagement after the Duchess' maternity leave.
The Duke and Duchess have been longtime supporters of mental health awareness, promoting their organization, Heads Together, to help mental health charities and groups around the country and the world. And so did William's jokes.
"Where can you hide it", Kate joked as she painted a white stroke, and which point Prince William said, "It's nearly ruined the picture", before adding, "No, this is probably how you ruin a picture" as he took his turn.
The Duke and Duchess had a chance to speak to young delegates at the summit about the challenges and issues they face.
Taylor Swift makes history at American Music Awards
Taylor Swift accepts Artist of the Year during the 2018 American Music Awards on October 9, 2018, in Los Angeles . She added that the awards represented "encouragement and motivation to be better and work harder".
DUP call Irish border plans a ‘disaster’ as summit looms
That could destroy relations between Mrs May and the DUP - which has warned it has a "blood red" line on the issue. A DUP source told Sky News: "It is unacceptable that we would be treated differently to the rest of the UK".
MI man's doorstop is $100,000 meteorite
A farmer who'd used a 23-pound rock as a doorstop since 1988 has learned that it's actually a meteorite worth $100,000 (£76,000). As the new owner of the property, the man was told that the rock was a part of the property and that he could have it.
They also heard presentations on two case studies of active mental health programmes from Slovenia and the United States of America and visited an exhibition area.
Middleton, who returned to her royal duties exactly one week ago to greet school children at a wildlife garden event, looked as stunning as ever for her latest engagement.
The couple also learned about Friendship Bench, part of an innovative programme from Zimbabwe, which has taught elderly women the skills to become trained 'community grandmothers'.
The couple is also preparing for another big event on Friday when William's cousin, Princess Eugenie, celebrates her Royal Wedding to fiance, Jack Brooksbank, at Windsor Castle.