The King waved to onlookers as he walked to church on the Sandringham estate in Norfolk on Sunday local time – his first public sighting since he was discharged from hospital.
Charles, 75, appeared in good spirits as he made the short walk to St Mary Magdalene Church, accompanied by the Queen.
He has been recuperating at his Norfolk home in England since last Wednesday, when he returned by helicopter from London.
He had been discharged from the London Clinic two days earlier after a three-night stay as he underwent treatment for an enlarged prostate.
The Queen, 76, who carried out four official engagements over four days last week, told well-wishers Charles was “recovering well” and was “getting on” and “doing his best”.