The King has been spotted smiling and waving to onlookers before going to church with the Queen.
The 75-year-old monarch has been staying at Sandringham, in Norfolk, after his first round of cancer treatment in London this week.
King Charles arrived at St Mary Magdalene Church and was seen holding an umbrella for Queen Camilla before being greeted by the Rev Canon Dr Paul Williams.
It comes a week after the monarch spoke for the first time since being diagnosed with a form of cancer while undergoing a procedure for an enlarged prostate.
Writing from Sandringham, the King said: “I would like to express my most heartfelt thanks for the many messages of support and good wishes I have received in recent days.
“As all those who have been affected by cancer will know, such kind thoughts are the greatest comfort and encouragement.”
Read more:
King’s cancer diagnosis: What we know so far
Queen’s support now more important than ever for the King
It also comes after Prince Harry hinted at a reconciliation with the royals after he came back to the UK to see his father.
Speaking to Good Morning America, the Duke of Sussex was asked if a family illness could have a “re-unifying effect”, and “is that possible in this case”?
The US-based royal, who stepped down from full time duties in 2020 and has since made a number of statements about his family, said: “Yeah, I’m sure.”