The search for a facile and energy-saving nanomaterial fabrication technology is of great significance in the area of energy conversion and storage. However, most approaches require high temperature heat treatment to transform nanomaterials from amorphous to crystalline phase or improve their crystallinity. This paper reports a hydrothermal approach for the synthesis of well-crystallized CuO hierarchical structures assembled by intercrossed nanosheets. Time dependent experiments suggest that CuO hierarchical structures followed a rapid nucleation and crystal growth mechanism. Therefore, well-crystallized CuO hierarchical structures can be directly applied as anode for lithium-ion batteries without further calcination. The results show that the uncalcined CuO hierarchical structures could deliver discharge capacities of 575 mA h g⁻¹ at 1C over 100 cycles and 504 mA h g⁻¹ at 2C over 100 cycles, respectively, which were much better than those of calcined ones. This excellent performance can be ascribed to a synergistic effect of their high crystallinity and hierarchical structure containing micro and nano features.