Field experiments were conducted during summer 2012 and winter 20012-13, at Agricultural College and Research Institute, Madurai (Tamil Nadu Agricultural University) to study the effect of pre-emergence application of Calotropis gigantea leaf extract spray on weed control in cotton. The results revealed that the pre-emergence application of Calotropis gigantea leaf extract spray at 30 % concentration followed by hand weeding on 40 DAS did not show any phytotoxic effect on cotton and recorded the lower weed density and dry weight and increased the yield in cotton under irrigated condition compared to lower concentration of Calotropis gigantea leaf extracts and un weeded control.