Abstract: An apparatus to control an air conditioner system and a method for controlling the same, in which an operational priority is given to an air conditioner or a ventilation system according to peripheral environment and a season such that the air conditioner and the ventilation system are selectively operated to provide optimum air conditioning environment. The method of controlling the air conditioner system including the air conditioner to cool and heat a room and the ventilation device to perform a ventilation operation includes detecting an outdoor temperature, determining a season by comparing the outdoor temperature with a preset reference temperature, and determining an operational priority relative to the air conditioner and the ventilation device based on the determined season.