The card, which has been shared by recipients via Instagram, reads: "The Prince of Wales thanks you so much for your very kind message of sympathy.
"His Royal Highness has been enormously touched by the many generous messages that have been received in recent days; they have provided great comfort at this very sad time.
"The Prince of Wales sends you his warmest thanks and best wishes."
The message of thanks wasn't the only one received by the royal fan.
The Earl of Wessex, Prince Edward, and Sophie, Countess of Wessex, sent a joint card of thanks.
The thank you note featured a much more recent photo of Philip and read: "Thank you for your kind message of condolence."
"We are extremely grateful for your thoughtfulness in writing at this sad time."
His Royal Highness Prince Philip passed away aged 99 on the 9th of April, 2021.
The Palace made the official announcement at the time, stating: "It is with deep sorrow that Her Majesty The Queen has announced the death of her beloved husband, His Royal Highness The Prince Philip, Duke of Edinburgh.
"His Royal Highness passed away peacefully this morning at Windsor Castle. Further announcements will be made in due course. The Royal Family join with people around the world in mourning his loss."