In the present study mustard stalk is used for production of activated carbon with potential application in removal of methylene blue dye in its aqueous phase prepared by chemical activation route using ZnCl2. Mustard stalk activated carbon (MSAC) was prepared at an activation temperature of 650ºC and using an impregnation ratio of 2.0 for 1.5 h of activation time. Different parameter such as initial methylene blue concentration, agitation time, pH and dosage of activated carbon were used for conducting adsorption studies in batch mode. MSAC was characterized using FESEM (field emission scanning electronic microscope) with EDX (energy dispersive X-ray spectrometer), and Brunauer-Emmelt-Teller (BET). The best fitted adsorption data was obtained by Langmuir isotherm model with an equilibrium adsorption capacity of 190.90 mg/g. BET surface area and total pore volume of MSAC were found to be 406 m2/g and 0.328 cm3/g, respectively.