Abstract: We report the preparation of activated carbon (AC) using phosphoric acid (H3PO4) as the activating agent from Pistacia Atlantic (PA) shell. The properties of AC were characterized by the scanning electron microscopy (SEM), nitrogen adsorption isotherm, low angle XRD and Fourier transforms infrared spectroscopy (FTIR). The obtained mesoporous activated carbon has a BET surface area of 1728.78 m2/g. Methylene blue (MB) was chosen as model dye compound to evaluate the adsorption behavior. The best conditions resulted in PAAC with a maximum monolayer adsorption capacity of 350 mg/g.