Batch adsorption experiments have been carried out for the removal of cationic dye, methylene blue from aqueous solutions by using Parthenium hystrophorous L. as biosorbent. The effect of major variables such as pH, initial concentration, adsorbent dose and contact time has been investigated for the sorption of methylene blue on the low cost adsorbent. Equilibrium data were fitted in Freundlich, Langmuir and Temkin isotherm models and their constants are determined. The data could best be explained by Freundlich isotherm with maximum adsorption capacity (q(o)) of 40.79mgg(-1). Kinetic modeling for methylene blue adsorption is done using pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It is found that the pseudo-second-order kinetic model most appropriately described the adsorption kinetics. The result indicates that the weed biomass can effectively be used for methylene blue removal from simulated aqueous solutions.