In the present study, tannin and 3-Aminopropyltriethoxysilane (APTES) functionalized magnetic nanoparticles (Tan-A-MNP (was synthesized and the adsorption of methotrexate (MTX) drug was studied. The surface morphology and characteristics of Tan-A-MNP was determined by FTIR, SEM, TEM and XRD analysis. The optimum values of the effective parameters such as pH, carrier dosage, drug concentration, contact time and temperature were determined. The maximum adsorption of MTX on Tan-A-Fe3O4 was obtained about 91% based on the optimum conditions. The FTIR and TEM analysis of Tan-A-Fe3O4 indicated that NH and OH groups play an important role in MTX adsorption. According to the study of equilibrium data and comparison of four types of isotherm models, Langmuir isotherm with adsorption capacity of 55.55 mg/L was the predominant model. So, monolayer adsorption of MTX was occurred. Pseudo second order kinetic model was more compatible with the equilibrium data than that of first order model. Intra-particle kinetic model also revealed that boundary layer effects can affect on the kinetic of drug adsorption. Thermodynamic analysis exhibited that MTX adsorption was endothermic and spontaneous.