Abstract: We synthesized magnetic ZnFe2O4 nanoparticles via one pot solvent free microwave assisted technique. Iron (III) nitrate nonahydrate and zinc nitrate hexahydrate as reactants were crushed in the presence of reactive reagents. Then, the prepared mixture was transferred into a domestic microwave oven with the power of 900 W for 20 minutes. Finally, the resulting compound was collected, washed several times with ethanol, dried at 80 °C for 24 h and analyzed. The constructed nano-sized zinc ferrite was characterized using powder x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersion of x-ray spectrometry (EDX). This technique is a simple, fast, environmental friendly and can draw a usable viewpoint for the synthesis of nanomaterials. The ability of the prepared product was studied on the removal of organic pollutant (Congo Red) from aqueous solution through adsorption mechanism.