Magnetic polymer nanocomposites containing different concentration of magnetite (Fe3O4) with poly (vinyl alcohol-co-acrylic acid) (PVA-co-PAA) were prepared by in situ chemical oxidative polymerization method. The effect of nanoparticles on the structural, magnetic and glass transition temperature of the composite was carried out by XRD, FE-SEM, VSM and DSC. Mechanical properties, temperature dependent AC conductivity and room temperature DC conductivity were evaluated. FE-SEM and XRD patterns revealed the uniform dispersion and structural regularity of nanoparticles in the copolymer. The magnetic property of copolymer nanocomposite shows ferromagnetic and super-paramagnetic behavior. Tensile strength, hardness and glass transition temperature of composites increased with the increase in content of nanoparticles whereas the elongation at break decreases. The AC conductivity increased rapidly with temperatures and it obeys power law. Values of activation energy for the AC conduction process of the composite and the Cole-Cole plot of impedance was also determined. DC conductivity of nanocomposite was higher than copolymer and the maximum conductivity was obtained for 15 wt of composite. Variation in DC conductivity with the addition of nanoparticles in PVA-co-PAA was correlated with theoretical conductivity based on Bueche, Scarisbrick and McCullough model. A new model for conductivity has been proposed which showed better agreement with the experimentally observed conductivity over a wide range of concentration of nanoparticles. (C) 2016 Elsevier B.V. All rights reserved.