The couple sent note cards across the nation with one of the official family portraits taken at the private ceremony - which took place on July 6 at Windsor Castle - printed on the front.
A photograph of the touching gesture was shared online by royal fan @loopycrown3 and reveals the message addressed to those who penned a letter of congrats to the family-of-three.
The note reads: “The Duke and Duchess of Sussex have been overwhelmed by all the incredibly kind cards and letters they have received on the occasion of Archie's Christening, and are so touched that you took the trouble to write as you did.”
“It really was most thoughtful of you and greatly appreciated by Their Royal Highnesses who send you their very best wishes.”
Alongside the image, the royal blogger wrote: “Wonderful thank you postcard from TRH the Duke and Duchess of Sussex, thanking me for sending my good wishes to Archie for his christening.”
Fellow Buckingham Palace enthusiasts quickly took to the post to praise Harry and Meghan for taking the time to reply to well-wishers.
“Your family is a beautiful breath of fresh air and love,” one follower wrote.
Another added, “Totally classy. So very royal.”
A fellow Instagram user, who also sent the couple a congratulatory message, said that she “can’t wait” to receive her note from the family-of-three.
The Duke and Duchess of Sussex’s first child, Archie, was christened at the Private Chapel of Windsor Castle in an intimate service officiated by Archbishop of Canterbury, Justin Welby.
Two images from the big day, both shot by royal photographer Chris Allerton, were shared by the couple via their official Instagram account.
While the second image, featured on the thank you note, shows the family-of-three in the castle grounds with Archie wearing a handmade replica of the Honiton christening gown - a traditional ensemble which has been worn by royal babies, including the Cambridge children, for the last 11 years.
Thankfully, royal fans won’t have to wait long to see the three-month-old once again as the Sussex family are preparing to embark on their debut royal tour of South Africa on September 28.