We present the development of flexible secondary alkaline battery with rechargeability similar to that of conventional secondary alkaline batteries. Multiwalled carbon nanotubes (MWCNTs) were added to both electrodes to reduce internal resistance, and a cathode containing carbon black and purified MWCNTs was found to be most effective. A polyvinyl alcohol–poly (acrylic acid) copolymer separator served the dual functions of electrolyte storage and enhancing flexibility. Additives to the anode and cathode were effective in reducing capacity fades and improving rechargeability.