Occupants of hospitals, as of other buildings, have widely differing thermal comfort requirements due to their different levels of clothing and metabolism. This study concerns three main groups of occupants in Iranian hospitals: patients able to be covered; patients not able to be covered, due to their medical conditions; and staff. The study investigated actual thermal comfort, as calculated for these various occupants in Iranian hospitals. The “actual thermal comfort” has been derived from monitoring those parameters that affect thermal comfort, in fourteen rooms in four separate Iranian hospitals. The “actual thermal comfort” calculated for each room has then been compared with Iranian and international recommended standards for acceptable thermal comfort. The results obtained in this study indicate a wide range of actual thermal comfort conditions in Iranian hospitals; overall the thermal comfort conditions recorded during the measurement period are felt to be unacceptable.