The polymerization of anilinium–dodecylbenzenesulfonic acid (DBSA) monomer in an aqueous medium in the presence of an organically montmorillonite (MMT) clay treated for nylon resulted in the formation of nanocomposites. The polymerization and conductivity behavior of the nanocomposites were studied. The intercalation of polyaniline (PANI)–DBSA into the galleries of the organo-clay was confirmed by X-ray diffraction analysis, and significantly large d-spacing expansions from 13.3 to 29.6 Å for the nanocomposites prepared at different conditions were observed. For comparison, a PANI–DBSA/untreated MMT composite was also studied. X-ray results for the latter showed that no intercalation has taken place. Thermogravimetric analysis demonstrated enhancement of the thermal stability of the nanocomposites relative to the bulk polymers.