The monarch, 75, appeared in high spirits as he arrived for the morning service at St Mary Magdalene Church located in Norfolk.
Prior to the service, Charles could be seen greeting Reverend Canon Paul Williams who shook hands with the royal and flashed a warm smile.
For the special occasion, His Majesty wrapped up warm in a cappuccino tweed coat complete with two large pockets on either side. He teamed his cosy outer garment with a pair of smart, charcoal-hued trousers, a crisp shirt, toffee suede brogues and a festive red tie.
Braving the cold, Charles also donned a pair of thick gloves and held onto a navy umbrella in anticipation of rain.
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The picturesque 16th-century chapel sits on the King's Sandringham estate which he inherited from his mother, the late Queen Elizabeth II.
Since her heartbreaking death, the King has continued his mother's tradition of spending Christmas at the estate, and attending church with his family on Christmas Day.
Sandringham is where the late monarch typically spent her winter break, residing there throughout the festive period before returning to London after the anniversary of her father King George VI's death on 6 February.
King Charles's Sandringham visit comes after he mourned the loss of a family friend: Queen Elizabeth II's loyal companion and former lady-in-waiting, Prudence, Lady Penn.
Lady Penn, also known as Prue, was the widow of Sir Eric Penn, the one-time Comptroller of the Lord Chamberlain's Office. Over the years, when she lived very close to Buckingham Palace, Prue had become a close confidante and family friend of the royals.
Aside from forming a friendship with Queen Elizabeth II, Lady Penn also enjoyed a close bond with Princess Margaret and the Queen Mother.
And when Charles became King, she confided to a friend on his Accession: "Have you noticed how our new Sovereign seems to have grown in stature overnight? He looks every inch a king.
"I am devoted to him and know that he will take on the mantle with sensitivity, wisdom, and strength."
Lady Penn was also appointed LVO in the 2002 demise honours list. She is survived by her two sons and a daughter.