The position was previously held by Queen Elizabeth II, who fulfilled the role for 67 years.
The Duchess of Cambridge's secret photography skills have been hiding in plain sight for years.
To celebrate the announcement, the Duchess stopped by Warren Park Children's Centre in Kingston-upon-Thames, south west London for a photography workshop run by the Royal Photographic Society and Action for Children, another of Kate's' patronages.
The Royal Photographic Society and Action for Children organisation ran the workshop along with photographers Jillian Edelstein and Harry Borden.
Kate also spent time with Josh Evans, nine, from Liverpool talking to him about his new found love of photography. Donning a subtle printed dress, the Duchess of Cambridge and mother of three was clicked with her youngest child, Prince Louis.
The queen's giving Kate a patronage that so closely aligns with her interests is a touching gesture. Maybe it's right in front of you, maybe far away, but choose your object and focus on it. Leave home with the camera.
CNN commentator Victoria Arbiter tells Yahoo UK's 'The Royal Box:' "I think we may see Kate and Meghan at Wimbledon together again, which would be great, it would be a lovely show of togetherness".
"She did not look at Kate as someone who was worthy of joining the Royal Family".
Meghan reportedly left Kate in tears after Princess Charlotte's bridesmaid fitting, and rumours began swirling over their rocky relationship.
The Duchess has been documenting milestones of their lives, such as their birthdays and their first days at nursery.
Most notably, the Duchess has become known for taking her own portraits of her children and releasing them to mark their birthdays.