An effective bi-functional electrocatalyst of Co3O4/Polypyrrole/Carbon (Co3O4/Ppy/C) nanocomposite was prepared through a simple dry chemical method and used to catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Three types of carbon support as Vulcan carbon, reduced graphite oxide (RGO) and multi-walled carbon nanotubes (MCNTs) were used to study the influence on electrochemical reactions. Spherical shaped Co3O4 nanoparticles with 8-10 nm was found uniformly distributed on Ppy/C composite, which were analyzed by X-ray diffraction and transmission electron microscopy techniques. Amongst, Co3O4/Ppy/MWCNT shows improved bifunctional electrocatalytic activity towards both OER and HER with relatively low over potential (340 mV vs. 490 mV at 10 mA cm(-2)) and Tafel slope (87 vs. 110 mV dec(-1)). In addition to that, MWCNT supported Co3O4/Ppy nanocomposite exhibits good electronic conductivity and electrochemical stability up to 2000 potential cycles. The results clearly indicate that the Co3O4/Ppy/MWCNT nanocomposite could be the promising bi-functional electrocatalyst for efficient water electrolysis. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.