Water scarcity is one of the most critical problems confronting many countries, including Egypt. One issue is that agricultural evaporative cooling systems use a lot of water, so water conservation is essential. The goal of this study is to alleviate pressure on freshwater uses in the agricultural sector by using saline water instead of freshwater for the evaporative cooling process. To achieve this objective, a wooden-framed greenhouse covered by a layer of single polyethylene sheet with a thickness of 130 μm was constructed to provide the environmental conditions for barley production during the summer season. Two sources of water (freshwater and seawater) were used to evaluate the use of seawater with an evaporative cooling system and investigate the impact of using seawater on the system's performance. The results indicated that the average indoor temperature ranged from 21.76 C˚ to 25.16 C˚ by freshwater with 71.90% and 60.68% average cooling efficiency and coefficient of performance of energy use, respectively while the average indoor temperature by seawater ranged from 22.18 C˚ to 25.81 C˚ with 68.08% and 59.09 % average cooling efficiency and coefficient of performance respectively. The results also revealed that the impact of seawater on the physical and chemical properties of barley and the system's performance was negligible when contrasted with the use of fresh water in evaporative cooling. This study demonstrates the viability of evaporative cooling with seawater, which is a significant benefit for evaporative cooling applied in specifically coastal areas for saving freshwater.