γ′-Fe₄N has attracted increasing attention in the field of magnetic and electrochemical catalysis due to its high saturation magnetization (208 emu g⁻¹), special metal-like properties, and unique crystal structure, which is similar to that of anti-perovskite. The introduction of another transition metal element, such as Co, Mn, or Ni, to replace the Fe atoms can optimize the magnetic properties, reduce magnetostriction, and enhance the thermal stability of iron nitride materials, as well as improve the electrocatalytic performance. (Fe_xNi_1−x)₄N nanoparticles (NPs) encased within amorphous carbon were prepared via a simple route that combines a solvothermal method with non-ammonia gas nitriding. The doping of Ni not only has an important effect on the magnetism, but it also enhances the electrocatalytic performance of the oxygen evolution reaction (OER). The saturation magnetization (M_s) of (Fe_0.95Ni_0.05)₄N NPs increased to 168.15 emu g⁻¹ compared with (Fe₁Ni₀)₄N (142.89 emu g⁻¹). Furthermore, (Fe_0.90Ni_0.10)₄N exhibited the best OER activity, showing an overpotential of 292 mV to deliver a current density of 10 mA cm⁻² and a low Tafel slope (29 mV dec⁻¹). These results indicate that the use of Ni-doped γ′-Fe₄N can lead to great improvements for magnetic material and electrochemical catalysis applications.