Matrix mediated synthesis of nanoparticles was utilized to prepare calcium phosphate nanoparticles with a size of 10 nm. The particles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Nanocomposites of polystyrene and nano-calcium phosphate were prepared by the melt-mixing technique. The composites were characterized by TEM to assess the dispersion of the nanoparticles. SAXS measurements of the composites and the fit with Beaucage model described the fractal dimensions of the particles. Mechanical properties of the composites significantly improved with the addition of nanofillers. Dielectric behavior of the nanocomposites was measured with respect to the filler content, temperature, and frequency. The dielectric constant increases with increase in temperature and decreases with increase in frequencies. Dielectric constant increased with filler content in all frequencies; however, lower frequencies showed marked effect. a-Relaxation of the composites from the dissipation factor of the composites showed higher values for the lower frequencies. Electrical conductivity increased with respect to the filler content and volume resistivity showed the reverse trend. The theoretical prediction of the dielectric constant showed close agreement with the experimental value. POLYM. ENG. SCI. 2012. (c) 2011 Society of Plastics Engineers