Abstarct: Using the latent heat of evaporation of water as a natural driving energy resource, indirect evaporative cooling (IEC) systems can decrease air temperature without increasing its moisture content. The performance of any evaporative cooling system is largely dependent on the structure and design of the heat and mass exchanger. By modifying the exchanger of the IEC system, air could be cooled below its wet bub temperature and towards the dew point temperature In this study an indirect evaporative cooler with cross-flow heat/mass exchanger was developed in this research by optimal design, material selection, experimental investigations and economic, regional acceptance analysis. A prototype heat/mass exchanger and the associated air cooler was designed and constructed in laboratory. Testing was carried out to evaluate the performance of the experiment prototype. The results indicate that the wet-bulb effectiveness of the prototype ranged from 97/5% to 135% for all test conditions. Energy efficiency (or COP) rated from 40 to 65/83. It is also found that the water consumption of the prototype can be less than popular evaporative coolers in Iran. This research also investigates the feasibility, economic and environmental potential of using this cooler in buildings in Iran. It is concluded that this cooler can achieve a higher performance (in terms of effectiveness and energy efficiency) than the typical evaporative coolers without adding too much cost. It is found that the effectiveness and energy efficiency of the heat/mass exchanger in the cooler are largely dependent upon geometries of exchanger, the intake air velocity, temperature, humidity and the working-to-intake air.