Activated carbons are prepared from the stem parts of Achyranthes aspera and Allamanda blanchetii plants and are investigated as adsorbents for the removal of malachite green dye from contaminated water. Various extraction conditions such as pH, initial concentration of dye, adsorbent dosage, temperature, agitation time and presence of co-ions are optimized for the maximum possible extraction of the dye. For analyzing the combined effect of these parameters on the removal efficiency of the adsorbents, a statistical optimization modelling is adopted. The adsorbents developed are characterized and the adsorption abilities are observed to be 40.0 mg/g and 53.0 mg/g for the active carbons of Achyranthes aspera and Allamanda blanchetii plants respectively. The mechanism of adsorption is studied using various isotherm models and found that Freundlich model describes well the adsorption process. Thermodynamic studies reveal the endothermic and spontaneous nature of physisorption. The kinetics of adsorption is well defined by the pseudo-second-order model. Desorption and regeneration studies of the spent adsorbents indicate that the percentage of extraction has not come down below 80.0% even after five regenerations for both the adsorbents. The validity of the methods developed are tested with real dye polluted industrial effluent samples.