A novel composite nanostructure of C-CoOx-C with CoOx nanoparticles embedded in N-containing porous graphite carbon nanofibers (CNF) is successfully prepared via sintering the electrospun polyacrylonitrile-cobalt acetate tetrahydrate nanofibers covered by a polypyrrole (PPy) sheath that were attained from the chemical vapor-phase polymerization of pyrrole monomers using concentrated nitric acid as both the dopant and oxidant for the first time. The unique configuration with a well-defined morphology possesses a large specific surface area and prominent conductivity contributed to by the catalysis of metallic Co and the external PPy-derived carbon envelope, which could facilitate effective electron transfer and rapid ion penetration in C-CoOx-C, thus improving its electrochemical performance. As expected, when employed as an electrode active material for supercapacitors, the resultant C-CoOx-C showed a more acceptable specific capacitance, better rate capability and higher cycling stability than individual CNF and CoOx nanoparticle-decorated CNF without the coating of a N-doped carbon layer from PPy (C-CoOx).