Polypyrrole (PPy)/Fe3O4 nanocomposites were in situ synthesized using chemical oxidative polymerization in an aqueous solution of FeCl3.6H2O, in presence of different Fe3O4 loadings (0%–16.52%). These composites were characterized through a 4 Probe electrical conductivity measurement technique, Fourier Transform infrared spectroscopy, energy dispersive X‐ray spectroscopy, scanning electron microscopy, X‐ray diffraction, thermo gravimetric analysis, and vibrating sample magnetometer. Results showed maximum electrical conductivity of 75.28 S/cm for the 2.52% Fe3O4 loaded nanocomposite and with improved thermal stability compared with the host PPy. Furthermore, a linear relationship between saturated magnetization Ms and % composition of Fe3O4 in the above nanocomposites was observed, showing 6.34 emu/g at 16.52% Fe3O4/PPy nanocomposite. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers