Sustainable water management has become more critical in recent years due to climate change and water scarcity, increasing its impact. The rainwater harvesting method is an old, simple, and environmentally friendly method for collecting and using rainwater for areas that have or will face water shortages soon. Rainwater harvesting is an essential alternative to ensure future food supply in agricultural production where water needs are essential. This study aimed to theoretically determine the collectible rainwater potential and to make a cost analysis in the greenhouses of Bursa Uludag University, Faculty of Agriculture, Agricultural Practice Center. In addition, its usability in production in the greenhouse was evaluated. According to the study results, the amount of rainwater collected on the greenhouse roofs examined is 229,612, 272,176, and 79,870 m3 for G1, G2, and G3, respectively. Among the crops in greenhouses, lettuce has the highest water consumption. Since greenhouse-numbered G3 has a larger area and more production is made, there is a need for more water consumption. Rainwater harvested periodically in the greenhouse can cover 35.7% of crop production in the first and 35% in the second periods. Annual harvested rainwater in the greenhouse provides 35.3% of the water consumption of the crop. The cost of rainwater systems designed for greenhouses is approximately 11,742 $, and the system's payback period is ten years.