The King was officially welcomed to Balmoral after hailing the British public's "extraordinary compassion" for people in need.
Charles, 75, donned a kilt in his own King Charles III tartan, along with red hose and a brown leather sporran, as he inspected a guard of honour from the Balaklava Company, 5th Battalion, The Royal Regiment of Scotland.
The monarch also stood for the national anthem before taking the time to greet locals who had gathered near the gates during the welcome ceremony.
The King was also accompanied by his equerry, Lieutenant Colonel Johnny Thompson, who switched to a less public-facing role last year.
Charles is set to host his family members in the coming weeks at his Scottish residence.
© GettyThe King's appearance comes after he released a message to mark World Humanitarian Day on Monday. He praised the British public for their "remarkable generosity" and never failing to step up for those in need as he marked World Humanitarian Day.
The Disasters Emergency Committee shared an update on its work with the monarch, which includes appeals to helping those in Afghanistan, Ukraine, Pakistan and Turkey-Syria, and areas it is closely monitoring such as Sudan and Gaza.
© GettyHe was presented with a photo gallery of 15 images from recent campaigns, including images of hot meals being handed to families displaced by conflict in Gaza, a Ukrainian family in a refugee shelter in Poland, and rescuers searching for survivors after the Turkey-Syria earthquakes.
Watch the moving video below…
The DEC is an umbrella group which brings together 15 leading UK aid charities to raise funds at times of crisis overseas.
In his heartfelt written message, the King said: "In the face of such unbearably difficult circumstances for so many, the British public never fail to step up and show extraordinary compassion to those in need.
"These images show just a fraction of the work undertaken by local and international humanitarians, volunteers and aid workers to help the member charities of the Disasters Emergency Committee."
© GettyThe King continued: "Set against the backdrop of conflict, climate change and natural disasters, I was particularly drawn to the recurring themes of hope and resilience running through these photographs.
"I can only express my warmest possible thanks for the remarkable generosity of the British public in enabling swift action to support those in the most desperate of conditions, and my particular admiration for those humanitarians who risk so much in the service of others."
© GettyLast year was the deadliest on record for humanitarian groups, with 280 aid workers killed in 33 countries, a jump of 137 per cent from 118 people the year before.
The United Nations General Assembly adopted a resolution designating 19 August as World Humanitarian Day (WHD) in 2008, five years to the day after a bomb attack in Baghdad, Iraq, which killed 22 humanitarian aid workers including the UN special representative of the secretary-general for Iraq Sergio Vieira de Mello.
