Hierarchical CoO nano/microstructures are synthesized via a hydrothermal method and a subsequent annealed process. When evaluated for use in lithium-ion batteries, hierarchical CoO nano/microstructures show a high initial discharge capacity of 1370 mAh/g and a high reversible capacity of 1148 mAh/g over 20 cycles at a current density of 100 mA/g. Superior rate performance with coulombic efficiency of about 100% upon galvanostatic cycling is also revealed. The excellent electrochemical properties of hierarchical CoO nano/microstructures make it a promising alternative anode material for high power lithium-ion batteries applications.