Intertwined composites of molybdenum trioxide and multiwall carbon nanotubes (MoO3-MWCNTs) were synthesized by a hydrothermal method for high performance electrochemical energy storage devices. Specific capacitance measurements revealed cycle dependent behavior, which was examined by cyclic voltammetry and impedance spectroscopy. The capacitive charge-storage properties of intertwined MoO3-MWCNTs were found to be superior to those of either MoO3 nanowires or randomly entangled mesoporous MWCNTs. This study showed that double-layer, faradaic and intercalation mechanisms are in operation in the charge storage process. This rather complicated mechanism causes irreversible structural modifications to the oxide lattice, which were verified systematically by various characterization techniques. The intertwined nanocomposites showed increased charge-storage capacity without compromising the charge/discharge kinetics in MWCNTs or MoO3 nanowires. The use of such intertwined nanocomposites is quite promising for electrochemical energy storage devices in portable electrical vehicles. (C) 2014 Elsevier Ltd. All rights reserved.