The never-before-seen family photo on the card shows Prince George seated on an outside bench next to William, with the backdrop of a big pile of wood.
WATCH: The Cambridges got into the festive spirit with a visit to the pantomime
The whole family is dressed in warm winter clothes, including cozy sweaters and outdoor boots.
The card is "To all the amazing NHS staff," with the message: "Wishing you a very Happy Christmas and New Year."
There is a handwritten note from William in the card as well. He writes: "We can never thank you again for all the dedication and sacrifice you have had to make this year. We will be forever grateful." The card is signed by William and Catherine.
It's been a big week for the Cambridges. On Friday William and Kate took all three of the children to an early Christmas treat- a trip to the pantomime.
The Duchess took children to watch Pantoland at the London Palladium Friday
William and Kate, in an Alessandra Rich dress, arrived hand in hand with their children to watch Pantoland at the London Palladium, joining a special performance hosted by The National Lottery for key workers and their families.
George, seven, looked all grown up in a red and navy striped sweater, while Charlotte, five, wore a sweet tartan dress and black tights, but appeared reluctant to hold her father's hand.
Louis, now two-and-a-half, wore a smart navy coat as the family arrived at the West End theatre for their first red carpet engagement as a family of five.
The family may have given out the card at this event
On Tuesday this week, the Duke and Duchess of Cambridge made a very special trip to Reading to meet nurses at the Royal Berkshire Hospital – which just so happened to be the hospital the Duchess was born at on 9 January 1982.
Graham Sims, chairman of Royal Berkshire NHS Foundation Trust, quipped to Kate: "Welcome back," as she arrived.
It is unclear if the beautiful family Christmas cards were gifted to NHS staff during a special portion of Friday's event to the pantomime, or if they were possibly gifted to NHS staffers during their hospital engagement earlier this week.
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