In this study, a simple and efficient method for removal of Cr (VI) from water samples was developed using modified nanoclay. A facile one-step method was employed to produce Dithizone-Montmorillonite (Dz-MMT) composite. The synthesized composite was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The effectiveness of the composite in Cr (VI) removal from aqueous solutions at different adsorbent dose, solution pH, contact time, and agitation rate were examined. The composite had a high uptake capacity in room temperature and removed Cr (VI) (10 mg/L) of about 98% from aqueous solutions by 3 g/L of adsorbent in 90 min. The equilibrium adsorption isotherm data are tested by applying both Langmuir and Freundlich isotherm models. The composite effectively removed Cr (VI) from water, and the maximum adsorption capacity obtained from the Langmuir equation was 76.9 mg/g. Adsorption kinetics of Cr (VI) on the composite followed the pseudo-second-order kinetic model. The method was applied to the removal of Cr (VI) in tap water, river water, and industrial wastewater samples from different parts of Khouzestan, Iran.