► Activated carbon was prepared from date pits by ferric chloride activation (FAC). ► FAC was used to remove methylene blue (MB) from aqueous solutions. ► Surface area of 780.06m2/g was characterized for FAC. ► Maximum MB capacity of 259.25mg/g was reported using Sips isotherm. ► The kinetic data were well described by pseudo-second order model. Ferric chloride has been utilized as an activator for preparation of activated carbon from an agricultural solid waste, date pits. The characteristics of prepared activated carbon (FAC) were determined and found to have a surface area and iodine number of 780.06m2/g and 761.40mg/g, respectively. Experiments were carried out to evaluate the batch adsorption isotherms and kinetics of methylene blue (MB) on FAC at different temperatures. Experimental equilibrium data were analyzed by the Langmuir, Freundlich and Sips isotherm models. The results show that the best fit was achieved with the Sips isotherm equation with a maximum MB adsorption capacity of 259.25mg/g. Pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial MB concentrations. The adsorption kinetic data were well described by the pseudo-second order model. The calculated thermodynamic parameters, namely ΔG, ΔH, and ΔS showed that adsorption of MB onto date pits was spontaneous and endothermic under examined conditions.