To investigate the effect of different irrigation levels on yield and yield components of two cotton cultivar, a two-year experiment (2006-2007) was carried out at Agricultural Research Center of Kabotarabad, Isfahan, Iran. In this experiment, the strip split-plot design, as randomized complete blocks with four replications, was used. Main plots consisted of six levels of irrigation (T1 to T6, based on cumulative evaporation from Class A pan, at three growth periods of cotton) and subplots were two cotton cultivars (B557 and Tabladyla). Results indicated significant effects of irrigation level on yield. The T6 treatment (irrigation at three stages: from four-leaf stage to early flowering, flowering until boll opening, and beginning of boll opening until the end of growth, based on 150, 70 and 110 mm cumulative evaporation from Class A pan) was superior to other treatments in terms of lint yield and water use efficiency (5113 kg/ha and 0.52 kg/m3, respectively). Higher boll weight and number per plant was the main reason for significant yield advantage in this treatment. Significant difference between the two experimental cultivars and interaction of cultivar and irrigation treatments, in terms of different traits, was not observed. B557 cultivar, with 3237 kg/ha lint yield in the first harvest, produced significantly higher yield than Tabladyla cultivar, with 2481 kg/ha lint yield. The results of this study showed that deficit irrigation at vegetative growth stage (four-leaf stage to early flowering) of cotton not only led to improved yield, but also saved considerable amount of irrigation water.