Hierarchical plush polypyrrole (PPy) layers intercalated graphene sheets have been prepared by in-situ intercalative chemical polymerization. The as-prepared graphene/PPy nanocomposites have been successfully characterized in terms of composition, morphology, and electrochemical properties. It was found that the chemically modified graphene nanosheets and in-situ polymerized PPy layers formed uniform nanocomposites with homogeneous PPy layers intercalated between the graphene substrates. Such uniform nanostructure together with the observed high conductivities (the highest 1980 S m(-1)) afforded the graphene/PPy composites with high specific capacitance and good cycling stability during the charge-discharge process when used as supercapacitor electrodes. The graphene/PPy (with optimized composition 10:1) based supercapacitors display intriguing performance with a maximum specific capacitance of 650 F g(-1) at 0.45 A g(-1) current density, a highest energy density of 54.0 W h kg(-1) at 1 mA current, and a highest power density of 778.1 W kg(-1) at 5 mA current. Furthermore, the graphene/PPy supercapacitor exhibits an excellent cycling stability with 95% specific capacitance retained after 5000 cycles. The impressive results presented here may open the window for grapheme/PPy composites for their promising applications in high energy density storage system. (C) 2013 Elsevier Ltd. All rights reserved.