Magnetic chitosan-modified CoFe 2 O 4 nanoparticles, CS/CoFe 2 O 4 , were successfully synthesized by an in situ coprecipitation technique. The structure, crystal phase, surface morphology and magnetic properties of CS/CoFe 2 O 4 were characterized by FTIR, TGA, XRD, FE-SEM, EDX and VSM analyses. The as-prepared CS/CoFe 2 O 4 nanoparticles were employed to adsorb Acid Yellow 17 dye (AY17) from aqueous solutions. The influence of experimental parameters, such as pH, temperature, contact time, adsorbent dosage and initial dye concentration on the efficiency of AY17 adsorption was studied. The maximum dye removal percentage reached 90% after 90 min adsorption at pH 4.0 and 323 K for the solution with an initial AY17 concentration of 30 mg L-1 and CS/CoFe 2 O 4 dose of 0.01 g. The adsorption kinetics agreed well with the pseudo-second order model. The isothermal data preferably followed the Langmuir model, with the maximum adsorption capacity of 89.10 mg g-1. Thermodynamic studies illustrated that the adsorption process is endothermic and spontaneous.