The purpose of this research is to explore the effect of textile properties on the microclimate inside the cap and subjective wearing sensations in various environmental conditions, with/without radiation or air current. Heat and moisture transfer properties of cap fabrics were measured and their relationships with the microclimate inside caps and with the subjective wearing sensations in three different environmental conditions were analyzed. Principal component analysis and regression analysis were employed for the relationship of microclimatic temperature and thermal comfort. The most important fabric properties affecting the cap microclimate in a hot environment was found to be those related to liquid moisture transport and emission. Properties related to vapor transport and air permeability did not affect the microclimate much in a hot environment without radiation or air current. However, in the radiation environment, fabric with high thermal resistance generated a microclimate with low temperature and humidity, thereby giving good thermal comfort. In the environment with air current, air permeability and its related properties were the most critical fabric properties influencing the microclimate and subjective thermal comfort. According to the regression models obtained, thermal discomfort sensation starts at around 33°C, and becomes very high at 35°C.