Novel hollow Ni0.2Mn0.8O1.5 twin microspheres were synthesized through a facile solvothermal reaction followed by calcination. The prepared hollow twin microspheres were composed of a large number of aggregated nanoparticles, with many pores homogeneously distributed across the whole of the twin microspheres. Benefiting from such structural advantages, such as the void core and high porosity, the prepared hollow Ni0.2Mn0.8O1.5 twin microspheres, as an electrode for supercapacitors, exhibited remarkable electrochemical performance with a large specific capacitance (491 F g(-1) at 0.5 A g(-1)), desirable rate capability (81% of capacity retention at 5 A g(-1)), and excellent cycling stability (94.6% of the initial capacity after 2000 cycles). Moreover, a fabricated asymmetric supercapacitor cell based on Ni0.2Mn0.8O1.5 and active carbon demonstrated an energy density of 19.5 Wh kg(-1) at a power density of 799 W kg(-1), suggesting a promising practical application for these microspheres in supercapacitors. Novel hollow Ni0.2Mn0.8O1.5 twin microspheres have been synthesized based on the oriented attachment and Ostwald ripening effects, demonstrating high energy density and power density for the promising application in energy storage devices.