Fuel cells (FCs) are promising electrochemical devices that convert the chemical energy of fuels directly into electrical energy, as long as the fuel is supplied. This paper describes a room-temperature hydrazine/air direct-liquid fuel cell (DLFC) based on the use of nanostructured copper electrodes. We show that nanostructured copper electrodes function as highly efficient and ultra-long-lasting catalyst for the electro-oxidation of hydrazine. Our Cu/hydrazine anodes show high electrical efficiency for long periods of continuous operation (more than 500h). A hydrazine/air fuel cell prototype was built with a nanostructured Cu/hydrazine anode, combined with a commercial air cathode. The output of this cell is about 0.45W at 1A (0.1Acm−2 corresponds to the anode area), and supplies about 2.3Wh and 1300Whkg−1 hydrazine. The hydrazine discharge efficiency is higher than 85%.