Herein, we describe a simple two‐step approach to prepare nickel phosphide with different phases, such as Ni2P and Ni5P4, to explain the influence of material microstructure and electrical conductivity on electrochemical performance. In this approach, we first prepared a Ni–P precursor through a ball milling process, then controlled the synthesis of either Ni2P or Ni5P4 by the annealing method. The as‐prepared Ni2P and Ni5P4 are investigated as supercapacitor electrode materials for potential energy storage applications. The Ni2P exhibits a high specific capacitance of 843.25 F g−1, whereas the specific capacitance of Ni5P4 is 801.5 F g−1. Ni2P possesses better cycle stability and rate capability than Ni5P4. In addition, the Fe2O3//Ni2P supercapacitor displays a high energy density of 35.5 Wh kg−1 at a power density of 400 W kg−1 and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles, whereas the Fe2O3//Ni5P4 supercapacitor exhibits a high energy density of 29.8 Wh kg−1 at a power density of 400 W kg−1 and a specific capacitance retention rate of 86 % after 1000 cycles. Ni2P and Ni5P4 with different microstructures and electrical conductivities have been successfully synthesized and both exhibit excellent electrochemical performance. Ni2P exhibits a high specific capacitance of 843.25 F g−1, whereas the specific capacitance of Ni5P4 is 801.5 F g−1. The Fe2O3//Ni2P supercapacitor displays a high energy density of 35.5 Wh kg−1 at a power density of 400 W kg−1 and long cycle stability with a specific capacitance retention rate of 96 % after 1000 cycles (see figure).