To improve the thermal and mechanical properties of polyimides, a nanocomposite of naphthalene containing polyimide (PI) was hybridized with Montmorillonite (MMT). The PI was synthesized from a diamine, 2,7-bis (4-aminophenoxy) naphthalene and polymerized with a 3,3’,4,4’-benzophenone tetracarboxylic dianhydride via thermal imidization. PI-MMT nanocomposites were then prepared from a DMAc solution of poly(amic acid) precursor and a DMAc dispersion of MMT which were organo-modified with various amount of n-dodecylamine. Characterization results demonstrated that the introduction of a small amount of MMT (up to 5%) led to enhanced thermal stability and mechanical properties of PI. The 5% weight loss temperature in N2 was increased by 46oC in comparison to pristine PI with an organoclay content of 5%. The CTE and dielectric constant were decreased. However, at organoclay contents higher than 5% these properties were reduced because the organoclay was poorly dispersed and resulted in aggregate formation.