Samantha Cohen, 51, handed in her notice as private secretary to the Duke and Duchess of Sussex in October.
She is set to embark on a new role at an eco-charity dedicated to reducing carbon emissions, according to the Daily Mail.
The staff member has taken a new job at Cool Earth, an organisation that aims to halt tropical deforestation.
One of the charity’s partners is the Royal Commonwealth Society, so it is likely Samantha - as a new co-chair of the board of trustees - will cross paths with the royal family in the future.
She has worked for Meghan, 38, and Harry, 35, since the departure of predecessor Edward Lane Fox in 2018, and recently accompanied them on their Africa royal tour.
She announced last year that she would be leaving after the birth of Archie, who arrived in May.
A statement on the organisation’s website, from trustee Mark Ellingham, read: “Cool Earth is delighted to welcome Samantha Cohen, former advisor to the Royal Household, as co-chair of its Board of Trustees.
“Samantha’s distinguished career ranges from working for the Australian Government to the Royal Household, where she was Assistant Private Secretary to The Queen from 2011-2018, and Head of Royal Communications prior to this.
"As she reaches the end of her most recent role as Private Secretary to TRH The Duke and Duchess of Sussex, Samantha joins Cool Earth with a wealth of professional experience and a personal passion for protecting the world’s forests.
"Samantha has been the driving force behind initiatives such as The Queen’s Commonwealth Canopy, of which Cool Earth is a managing partner.
“We are delighted to have Sam Cohen join Cool Earth, after playing such a key role in the creation of the Queens Commonwealth Canopy – an initiative that has done so much to protect forests around the world and to highlight the importance of its preservation and revival."
The mum-of-three, originally from Australia, has worked for the royal family for 17 years.
Her appointment comes as Harry and Meghan were were heavily criticised earlier this year for taking private jets, which are said by experts to be less environmentally-friendly than commercial planes.
However others have come to their defence, indicating their preference is for security reasons.
“Let’s be clear, all members of the Royal Family use private jets, they all use helicopters... they have got to get around and they have got to get around safely as well,” said Chris Ship, ITV’s royal editor to Yahoo UK’s ‘The Royal Box’.
“We don’t understand what it’s like being on a plane and people snapping you, taking pictures of you.“