A high thermal conductivity novolac/nickel/graphite nanosheet (novolac/Ni/NanoG) composite was synthesized through in situ polymerization. Graphite nanosheet (NanoG) was prepared by sonicating expanded graphite (EG) in an aqueous alcohol solution and was plated with nickel through an electrodeposition method. The X-ray diffraction spectrum shows that nickel was successfully plated onto the graphite surface and the nickel thickness is about 27.89 nm. The microstructures of the Ni/NanoG were characterized by scanning electron microscopy and transmission electron microscopy. The results reveal that nickel particles with the average diameter of 25 nm are coated on NanoG surface homogeneously and densely. Energy dispersive spectrometry spectrum confirms that the Ni content coated on NanoG surface, whose atomic percentage is 61%, is much higher than that of C element. The values predicted by theoretical model were underestimated the thermal conductivity of novolac/Ni/NanoG composites. Among NG, EG, NanoG, and Ni/NanoG four kinds of particles, the Ni/NanoG improved the thermal conductivity of novolac resin significantly. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012