 Herein, a facile solution-phase method is used to fabricate Mn3O4 nanowires. The structure, morphology and chemical composition of the crystals are characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. It is interesting that a morphology evolution can be induced by changing the reduction temperature, during which Mn3O4 nanoparticles and Mn2O3 nanostructures can also be obtained. Furthermore, asymmetric supercapacitor cell is utilized as a device to evaluate the capacitive performance by cyclic voltammetry and galvanostatic charge–discharge test. Electrochemical results show that the prepared Mn3O4 nanowire exhibits enhanced charge storage properties, which could promote its application in energy storage devices.