Due to their many novel physicochemical properties different from the bulk counterparts, zerovalent iron nanoparticles are of great potential in contaminants removal from waste water. Montmorillonite-supported zerovalent iron nanoparticles were prepared using borohydride solution reduction method. As revealed by combined spectroscopic and microscopic techniques, the resultant iron particles were nearly spherical core-shell entities (about 55 nm mean diameter) well dispersed on the montmorillonite surface, in which the shell (iron oxide) preserved the core (metallic iron) from complete oxidation in air atmosphere. Batch tests were carried out to investigate the adsorption of Cr(Ⅵ) by thus obtained composite. At the optimized solution pH of 1.0, the Cr(Ⅵ) uptake was mainly governed by the reduction of Cr(Ⅵ) to Cr(Ⅲ) at the interface of metallic iron, which could be accessed by Cr(Ⅵ) owing to the dissolved oxide shell in acidic media. The kinetics of the adsorption followed the pseudo-second-order model, the adsorption data fitted well with the Langmuir equation, and the adsorption was spontaneous and exothermic in nature. These results are important for developing advanced nanomaterials based on zerovalent iron and for their use in remediation of Cr(Ⅵ)-contaminated water.