The royals were captured on camera in a sweet video shared by Twitter user Hermesluv, which was reposted on royal fan account Packham Gown.
In the footage, Kate was seen with their new puppy, who appeared excitable as they walked across the garden to board the helicopter.
VIDEO: Kate Middleton opens up about youngest son Prince Louis
The Duchess looked stylish dressed in a long purple coat, while Charlotte appeared to be holding onto a miniature handbag.
William was seen holding Louis' hand, while George walked in between his brother and sister.
The family have delighted royal fans with several appearances over the past few days, along with the launch of their YouTube channel.
The Cambridges were spotted boarding their helicopter at Kensington Palace
In the latest video posted on the site, Kate gave a rare insight into her family life while chatting to four-year-old Mila Sneddon, who was pictured for the Duchess' Hold Still initiative.
The little girl, who is undergoing chemotherapy for leukaemia, was sepearated from her father in the first lockdown for seven weeks, after he had to go to work and didn't want to risk bringing coronavirus back to the family home.
During the chat, Kate told Mila how Louis, who recently turned three, has been charging around on his scooter. She said: "Louis has got so big now.
Prince William and Kate Middleton with their three children
"He's very quick running around and he’s on his little scooter as well. He's very quick. I can't keep up with him."
William, meanwhile, gave opened up about the family's celebrations for Charlotte's sixth birthday during a royal engagement last week.
The doting father was visiting the West Midlands on Tuesday and spoke to Jenna Jackson, the company's lead HR business partner and a mother-of-two, who asked him if Charlotte had enjoyed her birthday.
Kate recently opened up about how quickly Prince Louis is growing!
"She had a lovely day, thank you," said William. "Last year it was her birthday in lockdown but this year we were able to have one other family over."
The Duke also revealed Charlotte's hilarious response when anyone asks her age. He was heard joking in a video shared by MailOnline:
"If you ask her, she says she's 16." He added: "Charlotte says, 'I'm six now, I'll do what I do want.' They grow up very fast."
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