The playful prince donned a Santa hat and posed with delighted kids at Phelisanong Children's Home for his AIDS charity Sentebale.
In a nod to the festive season, Harry is pictured wearing a Santa hat with a group of similarly decked out beaming children.
Explaining the snap, he writes: "Festive cheer!
"Despite it being 32 degrees, someone gave out Christmas hats and inevitably one found its way onto my head.
"All the children, orphaned for one reason or another, absolutely loved the hats and balloons."
Writing about another image (above), where Harry is seen lifting three-year-old Lerato in the air, the 30-year-old said: "Wow, what a welcome we got!
"There were 40 over-energetic children using us as climbing frames, water fights, and a lot of laughs.
"The boy flying is Lerato, a three-year-old who was abandoned at birth. The photo was taken by three-year-old Karabo, who is blind.
"She heard the clicks, went to the camera and, with a little bit of help on direction, shot this great photo."
Keen photographer Harry also opened his own photo album from the five-day visit, releasing three black and white images showing portraits of people he met.
He said: "I have always enjoyed photography and the challenges that come with trying to capture the perfect shot, although privately I don't take many photos.
"The best photos I have are in my head - I have some very special memories, mostly from Africa.
"But on this visit, I had the time and opportunity to be on the other side of the camera and take some photos in the stunning country of Lesotho for my charity Sentebale."
Harry viewed construction of Sentebale's new Mamohato Children's Centre, which will provide care for vulnerable children living with HIV.
Showing that he has inherited his mum Princess Diana's famous compassion, Harry said: "These are children who have never had the chance to talk about their illness, and who had no idea that they were one of so many in their age group.
"It was really emotional watching them interact with each other.
"Some really outgoing chatty kids, others slightly overwhelmed, but all with huge smiles.
"This confirmed to me again that what we're doing is going to change thousands of children's lives, and hopefully save a generation."
Cathy Ferrier, CEO of Sentebale, said: "This visit was a great opportunity for Prince Harry to revisit Sentebale's work in country, meet the children and see the positive impact of our programmes.
"He also had a chance to put his personal input to the next phase of the building of the Mamohato Children's Centre."
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