Abstract By making use of cation-exchange approach, montmorillonite-Cu 2 S (MMT-Cu 2 S) nanocomposite was prepared and characterized. Its conductivity was found to be 3.03 × 10 −4 S m −1 . Pyrrole was introduced to MMT-Cu 2 S and polymerized within the interlayer to obtain MMT-Cu 2 S-polypyrrole (MMT-Cu 2 S-PPY) nanocomposite. The materials were characterized by XRD, FT-IR and ac impedance measurements. The conductivities of both materials were found to be mainly electronic as confirmed by the dc polarization analysis but the former has a slight ionic conductivity due to mobile protons. In the latter the negatively charged clay sheet serves as a giant immobile anion and hence has no ionic component for the conductivity. The electronic conductivity is 2.65 S m −1 .