A study was conducted to investigate the performance of three Bt (Bahubali, DCH-32 and Puli) and one non-Bt (DCH-32) cotton genotype against leafhopper Hischimonus physitis population fluctuation at AICRP on Cotton, Chamarajanagara, UAS, Bangalore during Kharif 2020-21. The incidence of leafhopper was observed from 30 th Standard Meteorological Week (SMW) and persists throughout cropping season. Peak population was recorded at 46 th SMW in all genotypes and highest mean incidence was recorded in Bhubali i.e., 9.51 per three leaves. Correlation study revealed that, Among weather parameters studied, maximum temperature, morning relative humidity showed significant positive effect and rainfall, number of rainy days had significantly negative on leafhopper population. Incidence of leafhopper was found equally in all genotypes studied indicating the possible influence of weather parameter.