The Present study was conducted to investigate the allelopathic effects of Kalmegh (Andrographis paniculata Nees) on seed germination, seedling growth and total biomass of wheat genotypes. Andrographis paniculata Nees by aqueous extracts at 0, 5, 10, 15 & 20 per cent concentrations under laboratory conditions. The allelopathic potentialities of leaf extract of Kalmegh decreased the seed germination with the rise of leaf extract concentration. The extract also inhibited in shoot and root length, GRI and vigour index of wheat genotypes and was maximum in susceptible genotypes (K1317 and GW322) followed by tolerant genotypes (HD2967 and HD2733). The decrease in sugars and protein level and increase in starch and amino acid level under aqueous leaf extract of Kalmegh were found to be related with tolerance and susceptibility of genotypes respectively. The results indicated that the allelopathic effect of leaf extract Andrographis paniculata on tolerant varieties of wheat was maximum in terms of all physiological and biochemical parameters.