In this study, flake-like polyaniline/montmorillonite (PANI/MMT) nanocomposites with rough surface were successfully prepared by in situ chemical oxidation polymerization during which poly(2-acrylamido-2-methylpropanesulfonic acid), a polymer acid, on the surface of clay platelets was used as dopant of PANI and played a 'bridge' role to combine PANI with clay. Flake thickness and surface roughness of PANI/MMT composites decreased with the increase of montmorillonite/aniline feeding ratio. The effects of operating parameters including pH, contact time, Cr(VI) concentration, and adsorbent dose were studied. The pseudo-second-order equation and three adsorption isotherms including Langmuir, Freundlich, and Temkin equations were applied to determine the adsorption rate and capacity. The results show that the flake-like PANI/MMT nanocomposites exhibited a high adsorption capacity (167.5 mg/g). The excellent adsorption characteristic of flake-like PANI/MMT nanocomposites will render it a highly efficient and economically viable adsorbent for Cr(VI) removal.