This study was conducted to determine water stress tolerance of two Iranian dudaim melons (Kerman & Birjand) and one Iranian muskmelon (Samsoury). Throughout the experiment, three different levels of irrigation with three irrigation starting points (-50, -65 and -75 cb of matric potential) were employed. Results indicated that water stress significantly affected yield, firmness, fruit sugars as well as leaf proline contents. Starting irrigation at -65 cb matric potential point caused no significant decrease on yield and yield components, indicating that it can be a modulate water stress for improving fruit quality in these crop plants. Also, interaction effects between water stress and genotype on mean fruit weight and on total soluble solids were observed as significant. Regarding these parameters, Samsoury was more reactive to water stress in comparison with the two dudaim genotypes. On the other hand, modulate water stress positively affected fruit sugars (Glucose, Fructose and sucrose). In conclusion, in similar conditions to theose in this experiment, with controlled water stress, such fruit qualities as total soluble solids can be improved without any significant decrease in yield.