Epoxy polymer nanocomposites (PNCs) filled with both barium titanate (BaTiO3) (500 and 100 nm) andconductive polyaniline (PANI) stabilized BaTiO3 nanoparticles (NPs) have been successfully prepared. Theeffects of the BaTiO3 nanofiller loading level and the PANI coating on the mechanical properties,rheological behavior, thermal stability, flammability and dielectric properties were systematically studied.The viscosity study on the nanosuspensions indicates that the PANI layer on the BaTiO3 nanoparticlesurface can promote the network formation of the epoxy resin. The introduction of the PANI layer wasfound to reduce the heat release rate and to increase the char residue of the epoxy resin. The dynamicstorage and loss moduli were studied together with the glass transition temperature (Tg) obtained fromthe peak of tan d, and the reduced Tg in the PNCs is associated with the enlarged free volume. Thetensile test indicated an improved tensile strength of the epoxy matrix with the introduction of theBaTiO3 NPs. Compared with the cured pure epoxy, the elasticity modulus was increased for all the PNCsamples. The fracture surface study revealed an enhanced toughness. Due to the ferroelectric nature ofBaTiO3, the real dielectric permittivity increased with increasing the BaTiO3 nanoparticle loading. ThePANI layer on the surface of BaTiO3 also enhanced the dielectric permittivity arising from the interfacialpolarization formed in the PNCs.