Ni-Fe-Co alloy coatings were obtained on mild steel substrates by electrodeposition from stable acidic citrate solution. The effects of plating conditions and cobalt content on the coating performance were investigated? and the optimal electrodeposition pro-cess parameters were obtained. The alloy coatings were investigated by scanning electron microscope, energy dispersive spectrometer, electrochemical impedance spectrum, polarization curve, and digital microhardness meter. Results show that the suitable processing parameters are 10 A/dm², 45 °C, and triammonium citrate of 10 g/L. The cobalt content of Ni-Fe-Co alloy coatings is increased linearly with increasing the cobalt ion content. The coatings have simple face-centered cubic solid solution structure. With increasing the cobalt content in the coating, the corrosion resistance and microhardness of coatings are increased firstly and then decreased. The Ni-Fe-13.51Co (wt%) coating exhibits the remarkable corrosion resistance: the charge transfer resistance is 3031 Ω·cm², and the corrosion current density is 5.754×10^-6 A/cm².