A field study has been conducted during two autumn seasons of 2012 and 2013 at Al-Anbar province to determine the actual water use by mungbean crop (Vigna radiata L.) under water stress conditions and potassium fertilizer, as well as the assessment of crop and vegetative growth characteristics. Four treatments of irrigation are used (I1 watering when %50 of available water used (treatment measure), I2 watering when %25 of treatment measure used, I3 watering when %50 of treatment measure used and I4 watering when %75 of treatment measure used) and three levels of potassium Sulfate fertilizer (41.5% K) (40, 80 and 120 kg. ha-1) in addition to the control (K0) are used, it is given K1, K2 and K3 to the potassium levels respectively. A split plot in randomized complete block design is used with three replications to do this experiment. Treatments of irrigation are used as main plots while potassium fertilizer levels are used as sub-plot. Least significant difference (LSD) at 5% probability is used to compare the means. The results showed superiority of the treatment of irrigation I1 in all characteristics (plant height and number of branches per plant, number of leaves per plant and leaf area and leaf area index) in the first and second seasons, respectively, do not differ significantly for the treatment of irrigation I2 and all the characteristics and two seasons, respectively. While fertilization treatment K3 showed its superiority in all characteristics, do not differ significantly for the treatment of fertilization K2 in leaf area in the first season, the number of branches and number of leaves per plant in the second season. The interaction among I1K3, I2K3 and I1K2 significantly give the highest means for all plant characteristics without significant differences.