The parents-of-three looked prim and proper as usual, with William wearing a dark suit, white shirt and blue tie. The brunette beauty looked elegant in a maroon coat-dress, matching headpiece and pointed-toe heels.
As the two made their way to the church, the smiling pair stopped to greet admirers who came to pay their respects.
Inside, the pair's demeanor was much more somber as they looked at a framed photo of the late monarch that rested beside a cushion and bouquet of flowers.
"A moment of reflection at St Davids Cathedral honouring Her Late Majesty and all that she did for communities like this around the UK, the Commonwealth and the world," read the caption of their Instagram post marking the moment.
Prior to the post, they shared a photo of the queen alongside the words, "Today we remember the extraordinary life and legacy of Her Late Majesty Queen Elizabeth. We all miss you. W & C."
Fans flooded the social media post with sweet sentiments, with one person writing, "Much love from America. Her Majesty is missed ❤️."
"Wonderful tribute to a truly remarkable woman! Sincere condolences to y’all!" said another.
"I'm sure they both miss her Majesty's guidance. I'm sure their children miss their GanGan 😢," commented a third, referring to Prince George, 10, Princess Charlotte, 8, and Prince Louis, 5, who didn't attended the gathering.
Never miss a story — sign up for the OK! newsletter to stay up-to-date on the best of what OK! has to offer. It’s gossip too good to wait for!
Though Prince Harry was in his home country to attend the WellChild Awards on Thursday, September 7, he didn't attend the service. However, as OK! reported, he did stop by St. George's Chapel in Windsor Castle on Friday.
The Duke of Sussex isn't expected to see any of his family members while he's in town due to their ongoing rift.