Polyvinyl-acetate/-cobalt (PVAc/Co) composite films were prepared using a casting technique. The structural and physical properties were studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, dielectric measurements, direct current magnetic susceptibility (?dc), and electron spin resonance (ESR). The XRD patterns revealed that the incorporation of Co particles increases the amorphization of PVAc and Co oxide formations. The DSC results suggest that the thermal properties obviously improved. Frequency and filler concentration dependence of the dielectric constant (e') and AC conductivity (sAC) were measured at room temperature in the frequency range 20 Hz to 3 MHz of pure PVAc and PVAc/Co composite films. The dielectric constant shows usual dielectric dispersion behavior. The dielectric constant and AC conductivity increased with the increase in Co content. The variation of sAC is attributed to hopping of polarons and bipolarons in the composites. The filling level dependence of the effective magnetic moment (mu eff) has been evaluated. The ESR spectra exhibit a peak of an increasing depth as Co content increases. The control of thermal stability, dielectric and magnetic moment of the composites films is interesting for applications such as electric and magnetic sensors. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012