Kate and her two sons are perched on a fork in the tree, while Charlotte is perched on a separate branch.
The family were casually dressed for the outdoor photoshoot.
Matt Porteous, a royal photographer, has photographed the Waleses at significant points in their lives.
Other members of the Royal Family also marked Mother’s Day with sentimental posts.
Sarah, Duchess of York, shared a sentimental post shining the spotlight on her daughters, Princess Beatrice and Princess Eugenie.