In this research, the preparation of nanoparticles of Fe0 (nano-zerovalent iron, NZVI) as adsorbent is discussed and the capability of adsorbing methylene blue (MB) is studied. The morphology of the adsorbent was evaluated with transmission electron microscopy. Batch studies were performed to delineate the influence of various experimental parameters such as pH, adsorbent dosage, initial dye concentration, temperature and contact time. Optimum conditions for MB removal were found to be pH 9.5, adsorbent dosage of 0.5 g L−1 and equilibrium time of 1 min. The experimental equilibrium data were adjusted by the adsorption isotherms from Langmuir and Freundlich models, and their equilibrium parameters were determined. The adsorption of MB dye by NZVI obeyed both the Freundlich and Langmuir isotherm. The adsorption capacity of NZVI for MB in terms of monolayer adsorption was 208.33 mg g−1.