To investigate the effect of water treatment and plant density on yield and yield components of two cotton cultivar, a two-year experiment (2006-2007) was carried out in Esfahan Agricultural Research Center. The use of a split plot factorial based on complete block with four replications for study. Two irrigation levels 135 (I1) and 180 (I2) mm of cumulative pan evaporation Class A, from flowering stage to the end of growth were assigned as main plots and treatment combination of two varieties of Mehr and Oltan of cotton and plant spacing 12, 15 and 18 cm (respectively, 120.95 and 80 thousand plants ha-1) were assigned made up as subplots. The results showed that both cultivars Mehr and Oltan in the density of 95 thousand plants per hectare in I1 irrigation treatments, respectively, with 2805 and 2745 kg ha-1 of yields produced the highest levels of yield compared to other treatments. In the I2 irrigation treatment and 95 thousand plants ha-1 density, Oltan cultivars producing 2119 kg ha-1, and had lowest yield compared to other treatments. In both cultivars in 95 thousand plants ha-1, between the two treatments of irrigation levels, no significant differences in terms of leaf dry weight. The results showed that irrigation after flowering phase until the end of growth, based on 135 mm evaporation basin A and the density of 95 thousand plants ha-1 can be proposed, for both cultivars studied.