Uniformly stacked nanosheets of Mn3O4 with different sizes and crystallinities have been self-assembled on a titanium substrate by a simple and scalable strategy. When the prepared Mn3O4 nanosheets are applied as electrode materials for supercapacitors, they exhibit enhanced electrochemical performances due to the high utilization of active materials. More significantly, based on these stacked nanostructures, we have discussed the relationships between specific area, crystallinity and the electrochemical performance of this material. The stacked nanostructures exhibit a high specific capacitance of 398 Fg−1 at a scan rate of 0.005 V s−1 over a potential window from −0.1 to 0.9 V with high rate capability and good cycling stability. These results demonstrate the importance of a well-arranged and stacked architecture of Mn3O4 in high-energy-storage applications.