Year-round air and ground-surface temperature-monitoring indicated occurrences of mountain permafrost in the Hidaka Mountains, southern Hokkaido. The results of air temperature monitoring indicated that the temperature condition in the summit areas of the Hidaka Mountains is similar to that of the lower marginal limit of the discontinuous permafrost zone. Monitoring of the ground-surface temperatures shows that ground thermal regimes vary spatially with snow cover duration and thicknesses, and surficial materials. The permafrost underlies coarse blocky materials covered with thick seasonal snow cover within the Pleistocene cirques. These conditions suggest that mountain permafrost in the Hidaka Mountains is categorized as Mountain Side Permafrost (MSP), which is found beneath mountain slopes covered with thick seasonal snow cover where the mean annual air temperature is lower 0°C. The major controls on permafrost development and preservation are ground cooling before the onset of snow accumulations and cold air concentration through blocky materials. The presence of funnels emitting warm air throughout winter indicates that the cold air circulation plays an important role in the development and the preservation of MSP.