Transition metal phosphides with excellent performance are one of the effective alternatives to noble metal catalysts in overall water splitting. In this paper, the Fe-NiCoP-MoO3 composite was prepared by a facile synthesis as the bifunctional electrocatalyst. Fe-NiCoP-MoO3 achieves an operating current density of 10 mA/cm2 at a low overpotential of 65 mV for hydrogen evolution reaction and drives an operating current density of 50 mA/cm2 at only 293 mV for oxygen evolution reaction. Significantly, Fe-NiCoP-MoO3 was employed as the anode and cathode for overall water splitting, which only requires a cell voltage of 1.586 V to reach 10 mA/cm2 as well as shows excellent stability. The electrocatalytic activity of Fe-NiCoP-MoO3 exceeds most of the recently reported typical bifunctional electrocatalysts. This may be due to the coupling effect between the polymetallic phosphides. In addition, heterogeneous catalysts generally expose more active sites than homogeneous catalysts. In addition, replacing MoO3 with WO3 and VO3 can also improve the performance of Fe-NiCoP. This work provides an idea for the modification of phosphides.