The present work deals with the preparation of CuO, polyaniline (PANI) and PANI-CuO nanocomposite by in-situ emulsion polymerization which is subsequently dispersed in water to get PANI and PANI-CuO nanocomposite based nanofluid to study its convective heat transfer performance. The enhancement in the convective heat transfer of PANI and PANI-CuO nanocomposite based nanofluids was investigated by adding 0.1-0.5 volume% PANI and PANI-CuO nanocomposite particles individually (having particle size less than 100 nm) in deionized water (basefluid), respectively. Further, the effect of percentage of PANI and PANI-CuO nanocomposite particles and inlet temperature, on convective heat transfer performance was investigated. The experimental results show an enhancement by more than 12% and around 38% in heat transfer coefficient, when 0.5 vol% of PANI and PANI-CuO nanocomposite particles were added to the base fluid, respectively. This is attributed to use of PANI encapsulated CuO nanocomposite particles in nanofluids, which enhances the heat transfer coefficient significantly compared to PANI nanoparticles alone in nanofluid. (c) 2016 Elsevier B.V. All rights reserved.