In this study, the adsorption properties of spinel ferrite-based adsorbent, CoFe1.9Mo0.1O4 (CFMo), for the removal of methylene blue (MB) from aqueous solution were investigated. Sol-gel process was successfully employed to prepare CoFe1.9Mo0.1O4 magnetic nanoparticles. The synthesized adsorbent was characterized by Fourier transform infrared (FTIR), scanning electron microscope (SEM) and X-ray diffraction (XRD). The adsorption experiments were carried out at various operational conditions (solution pH, initial dye concentration, contact time, adsorbent dosage and temperature) to evaluate the potential adsorption property of CFMo magnetic nanoparticles. The results showed that, under the optimum adsorption parameters, approximately 95 % of MB dye can be removed. The adsorption data were described by Langmuir isotherm model and the maximum amount of MB adsorbed was about 20.45 mg/g. Several adsorption kinetic models and thermodynamic parameters (G   , H   , S  ) were used to fit the adsorption experimental data. The adsorption kinetics followed the pseudo-second-order model (PSO), while the thermodynamic parameters indicate that the proposed adsorption process was endothermic and spontaneous in nature. The obtained results suggest that CFMo is promising adsorbent material for the removal of very toxic dyes from aqueous solutions.