Nano composites of poly(vinylidene difluoride) (PVDF)-polyaniline (PANI) were prepared by spin coating method. Also, the influence of PANI doping (20, 30 and 40% by weight) on the microwave dielectric parameters was investigated. The structural aspects of samples were studied by atomic force microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Dielectric properties of PVDF: PANI composites were characterized as a function of composition and frequency. The microwave dielectric constant increased smoothly with an increase in the concentration of PANI. Moreover, when the PANI content reaches 40 wt.%, there is a transition from an insulator to semiconductor. (C) 2012 Elsevier B.V. All rights reserved.