And the little girl was in need of a cuddle from the elegant royal after bumping her arm while playing on a bouncy castle.
Ever the attentive mother, Mary scooped the little girl up in her arms to quickly soothe away her tears.
And soon three-year-old Isabella was back happily playing with her brother Prince Christian, four.
Mary, elegant in a chocolate-hued minidress was taking her little ones to the annual Circus Summarum event in Copenhagen.
The Tasmania-born royal and Crown Prince Frederik have always maintained that they want their children to enjoy an ordinary childhood.
That means no nannies and a hands-on approach, which was clearly evident during this family outing.