sweet melon is an important crop in Egypt in terms of cultivated area, total production, and consumption, whether domestic or export, in addition to its high nutritional value and high water content. One of the main reasons that hinder the horizontal agricultural expansion is the shortage of irrigation water. Therefore, this study was conducted under the drip irrigation system to legalize the use of irrigation water and increase water use efficiency through evaluating the number of sweet melon inbred lines that could maintain an acceptable level of productivity and quality characteristics under water shortage conditions. Seven inbred lines (genetic material) of sweet melon named: New Matrouh line (L1), Mass Matrouh line (L₂) as a local ecotype, orange line (L₃), Sandafa line (L₄) as a local ecotype, Primal line (L₅), Ideal line (L₆)  and Kooz Assal Assuit line (L₇) as a local ecotype were planted under drip irrigation system during the summer seasons of 2017 and 2018. The experiment took place at the Experimental Farm, Faculty of Agriculture, Saba-Basha, Alexandria University, Egypt. Three irrigation rate treatments (40%, 70%, and 100% of ET₀₎ were performed. The gained results revealed that the best results for plant length (cm) trait were achieved with the treatment of 100 % of evapotranspiration. Many branches/plant traits scored the highest mean values with the treatment of 40 % of evapotranspiration. Total fruit yield/plant (kg) character and its component traits [ no. of fruits/plant and average fruit weight (g)] were significantly affected by both studied variables (sweet melon genotypes and irrigation rates). As for the main effect of irrigation rates on total fruit yield/plant (kg) and its component traits, there is a significant and direct proportional relationship between the independent variable (irrigation rates) and dependent one (studied characters) during the two studied seasons. The significantly highest mean values for total fruit yield/f were scored at 100 % of irrigation rate during the two seasons, followed with the treatment 70 % of irrigation rate; while 40 % of irrigation rate treatment possessed the lowest mean values in this respect. Most studied fruit characteristics were not significantly affected by different tested irrigation rates from 100% down to 70%.  The significantly lowest values for fruit characteristics were scored at 40% irrigation rate treatment. The results of the irrigation water use efficiency (IWUE) of the tested lines proved that the line Ideal (L₆) is the best line under the conditions of irrigation shortage supply. Through the gained results over the two seasons of this investigation, it is recommended to select the inbred line "Ideal" (L₆) because it is characterized by high productivity (kg/plant) at 100% irrigation rate or when there is a shortage of water supply (70% or even 40% of evapotranspiration) compared with other tested sweet melon genotypes; In addition to, its distinctiveness, to some extent, in their fruit characteristics.