In this study, we present the first application of magnetic Fe3O4 functionalized with activated carbon (Fe3O4/AC) as nano-adsorbent for the removal of gas-phase toluene by adsorption process. Magnetic Fe3O4/AC was synthesized via co-precipitation method within the framework of nanotechnology principles. Then, the effects of process conditions such as contact time, initial toluene concentration, and temperature on the adsorption capacity of toluene by the magnetic Fe3O4/AC were investigated using the response surface methodology (RSM). The obtained magnetic Fe3O4/AC was characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis. The maximum adsorption capacity of the magnetic Fe3O4/AC for the adsorption of the toluene was determined as 312.99 mg g-1 under optimal process conditions such as 59.48 min contact time, 17.21 mg l-1 initial toluene concentration, and 26.01°C temperature. The adsorption by the magnetic Fe3O4/AC indicated the best fit with the Langmuir isotherm model, and obeyed the pseudo-second-order (PSO) kinetic model. This study indicated that magnetic Fe3O4/AC could be applied as an adsorbent for the removal of gas-phase toluene.