The Duke of Rothesay, as he is known when in Scotland, attended the event in his role as chieftain.
He watched traditional Highland games competitions such as the three-legged and egg and spoon races. He then presented a trophy to the winning tug o'war team.
About 400 people attended the games on Saturday.
It is usually staged in a field nearby to Castle Mey, the late Queen Mother's Scottish home in Caithness, but was instead held at a field in John O'Groats due to the usual setting being water-logged.
Prince Charles drove to the event himself and was wearing traditional Scottish dress.
He appeared to be in high spirits whilst watching a mock horse dressage with participants prancing around on a wooden hobby-horses.
Prince Charles has umpired a tug o'war competition during a visit to the Mey Highland Games.