The iron-oxide nanoparticles (IONPs) filled multi-walled carbon nanotubes (IONP-MWCNTs hybrid) were directly synthesized via chemical vapour deposition method with acetylene as a carbon source. The bare IONPs were synthesized by hydrothermal method and the prepared bare IONPs were employed as a catalytic-support as well as a filling agent for the synthesis of IONP-MWCNTs hybrid at about 800 degrees C under atmospheric pressure. The synthesized IONP-MWCNTs hybrid was characterized by various physicochemical techniques including X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results demonstrate that the carbon nanotubes were successfully generated on the IONPs with the high yield because of unique carbon-iron metal interactions. An average diameter of synthesized IONPs and MWCNTs are around 9 and 50 nm, respectively. In addition, the HRTEM images and Raman spectrum confirms the obtained IONP-MWCNTs hybrid is well graphitic without major carbonaceous impurities. The electrochemical activity of the synthesized IONP-MWCNTs hybrid was performed in 2 M KOH using a three-electrode cell setup with a saturated Ag/AgCl as a reference electrode and a platinum plate as a counter-electrode by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. This electrode active material (IONP-MWCNTs hybrid) possess excellent supercapacitive behaviour and has excellent cyclic stability, even after 5000 cycles of charge-discharge at 4 A g(-1) as current density. Thus, the synthesized IONP-MWCNTs hybrid will be a suitable as well as an economical electrode active material for high-performance supercapacitors. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.