A hybrid of MnO2-nanowires and MWCNTs to be used as cathode in a supercapacitor with good electrochemical performance was prepared by a facile hydrothermal method. In this hybrid the α-MnO2 nanowires are well entangled with MWCNTs. The MWCNTs provide a network for fast electron transport whereas MnO2 nanowires show a fast redox response. Since gain/loss of both electrons and ions can be realized very rapidly at the same time, the hybrid has an excellent rate capability and delivers an energy density of 17.8Whkg−1 at 400Wkg−1, which is maintained almost constant even at 3340Wkg−1 in 0.5M Li2SO4 aqueous electrolyte. The cycling behavior is very good even in the presence of oxygen. The data present great promise for the hybrid as a practical cathode material for aqueous supercapacitor.