Polyaniline (PANI)/polyvinyl alcohol (PVA) nanocomposites has been prepared . Scanning electron microscopy, SEM of pure PVA and PANI/PVA nanocomposite films to monitor the morphology and dispersion of PANI on the surface of the PVA films. Positron annihilation lifetime measurements were carried out, in the air, at room temperature with a conventional fast–fast coincidence spectrometer. Dielectric permittivity , dielectric loss and AC conductivity of PANI/PVA nanocomposites has been achieved in the range of frequencies 40 Hz–5 MHz and temperature range of 293–353 K. It was found that; O-ps lifetime, τ ₃, its intensity, I ₃ and relative fractional free volume, F _r increase as the PANI content increases. The dielectric permitivity and loss increase with increasing the PANI content and decreases as the frequency increases. The values of the frequency exponent for the correlated barrier hopping and the binding energy of the charge carriers for the investigated nanocomposites decrease with increasing PANI content. Finally, the dielectric permittivity was found to be directly proportional to the relative fractional free volume, F _r .