The parents-of-three concluded their caption by asking, "What will you be doing to take care of your mental health today?"
In their post, the Cambridges tagged the Mind Charity, the Anna Freud National Centre, South Africa's Federation for Mental Health, Place2Be, Mental Health America, SANE Australia, Shout 85258, YoungMindsUK, the Mental Health Foundation of New Zealand and the Canadian Mental Health Association.
Kate and William have been mental health advocates for years, launching the Heads Together organization in 2016 alongside Prince Harry.
"Too often, people feel afraid to admit that they are struggling with their mental health. This fear of prejudice and judgement stops people from getting help and can destroy families and end lives," their mission statement reads. "Heads Together wants to help people feel much more comfortable with their everyday mental well-being and have the practical tools to support their friends and family."
"Heads Together is a mental health initiative spearheaded by The Royal Foundation of The Duke and Duchess of Cambridge, which combines a campaign to tackle stigma and change the conversation on mental health with fundraising for a series of innovative new mental health services," reads the website.
The Duke of Cambridge noted of their achievements, "Through our work with young people, emergency response, homeless charities, and with veterans, we have seen time and time again that unresolved mental health problems lie at the heart of some of our greatest social challenges."