In order to enhance its cationic sorption capacity, waste sawdust was functionalized by monosodium glutamate (MG) to produce potentially biodegradable cationic sorbent. The crude sawdust (CS) and functionalized sawdust (FS) were compared for the sorption behaviors against methylene blue (MB) in a batch system. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, contact time, and temperature etc.) were investigated and the sorption kinetic and thermodynamic characteristics were elucidated. The MB removal ratio on CS and on FS increased as the initial pH increased, and reached to the maximum value beyond pH 5 and pH 6 for FS and CS, respectively. For 250 mg/l of MB solution, a removal ratio of greater than 95% could be achieved with 2.0 g/l or more of FS. The MB removal percentage decreased more significantly on CS than on FS with increasing initial MB concentration. The isothermal data of MB sorbed on CS and on FS followed the Langmuir model and the sorption capacities ( Q_m ) of CS and FS for MB were 87.7 and 188.7 mg/g, respectively. The MB removal on FS and on CS reached to the equilibrium at about 10 and 36 hr, respectively. The MB sorption processes on FS and CS followed the pseudo-first-order rate kinetics. The sorptions of MB on CS and on FS were spontaneous and exothermic processes, and lower temperatures were favorable for the sorption processes.