"And then they were five," Tweeted Mette-Marit with an adorable image of the young labradoodles.
"Currently, there are seven," was the caption that then accompanied another picture on the Norwegian royal family's official Facebook page, Kongehuset, showing that yet more puppies were joining the royal household.
A staggering 7,061 people then liked the photograph and more than 400 leaving messages of congratulations.
Princess Mette-Marit and her husband Prince Haakon announced the happy news that their family dog was to have puppies via their Facebook page last Monday.
"The Royal Family is pleased to report that the family dog, Milly Kakao, is to have puppies," read the post, which was shared with the royal family's 74,177 fans. "They are expected on14 June.
"Milly is doing well and sleep a lot," it continued. "Dad is an exceptionally handsome and elegant gentleman named Snorri."
"The whole family is excited about," the message concluded, referring to Crown Princess Mette-Marit and Prince Haakon, both 39, along with their children Ingrid Alexandra, 9, Sverre Magnus, 7, and Mette-Marit's eldest child from her previous marriage, Marius Borg Hoiby, 16
Mum-of-three Mette-Marit also took to Twitter to share a picture of a scan of their dog.
"Not much time to slow down this week with 9 puppies plus on their way!!!" wrote the Norwegian Princess.
The family are very fond of their pet, who appears to be the sixth member of their close family. Milly even joined the Norwegian royals to celebrate National Day in Oslo, when the whole family dressed in traditional Norwegian clothing, posing with Milly, who wore a ribbon with the country's three national colours.
As busy as she is, the pretty blonde Princess found time to pay tribute to an important anniversary on Tuesday: "Today we are celebrating the 100th anniversary of women's right to vote in Norway. A humble thank you to all the pioneers who got us there."