The contamination of water resources with hexavalent chromium is a major environmental threat due to its mobility, toxicity, and carcinogenicity. Various methods have been developed and applied to remove Cr(VI) from polluted water, but their use in groundwater treatment remains limited. In-situ remediation of Cr(VI)-contaminated groundwater using nanoscale reducing agents such as nano zero-valent iron (nZVI), presents a low-cost, efficient, environmentally friendly, easy-to-implement solution. In this study, nanoscale zero-valent iron was successfully synthesized by reducing Fe(III) ions in FeCl3 solution with NaBH4 and applied to remove Cr(VI) from an aqueous solution. The prepared nanoparticles were characterized using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). The effect of contact time and initial pH value on the removal efficiency of Cr(VI) by nZVI was studied. Response surface methodology (RSM) was employed to develop a mathematical model, determine the influence of working parameters, and optimize the removal process. The characterization showed that the produced material was pure iron in a zero oxidation state and comprised spherical nanoparticles with diameters of less than 70 nm, which were aggregated into chains. The results showed that the Cr(VI) removal efficiency by nZVI improves with the increase of contact time as well as with the decrease of the initial pH value. The utilized RSM model appropriately predicted the removal efficiency with a high correlation coefficient (R2) of 0.9675. The optimal removal efficiency was 93.5% at the initial pH value of 5.0 for 241 min.