Weeds have always been considered strong competitors of crop plants; and today, they form an inseparable part of agronomic systems and inflict losses on crop plants. A field study was undertaken at Agronomy Research Farm, Islamic Azad University during 2011-12 to appraise the efficacy of some post spectrum herbicides against weed growth and their influence on growth and yield of broad bean. Treatment consisted of (1) and (5) Imazthapyr SL 10% 0.4 applied POST, with two control plots weed-free and weed-infested throughout the crop cycle, respectively. The experiment was replicated forth in a randomized complete block design. Compared with the weedy check, application of herbicides reduced weed biomass and increased broad bean biological and seed yield. Among herbicide treatments, imazthapyr with dose of 0.6 L haG 1 reduced weed dry matter by 98.7% and the lowest weed dry matter was observed with this treatment. Maximum broad bean biological yield was obtained in weed free check that was significantly different from other treatments. In comparison, among herbicide, maximum seed yield obtained with application of imazthapyr with dose of 0.6 L haG 1 , however, there was no statistical difference in seed yield among herbicide treatments.