Non-noble metal catalysts for photo/electrocatalytic water splitting are quite feasible for solving the problems of growing energy demand and environmental pollution. In this paper, noble-metal free Mn-Cd-S@amorphous-Ni3S2 hybrid catalyst (MCS@a-Ni3S2) with bifunctionality of photocatalytic hydrogen evolution and electrocatalytic OER is designed and prepared by simple hydrothermal method. The characterization results show that Mn-Cd-S was composed of cubic manganese sulfide and manganese doped cadmium sulfide, and amorphous Ni3S2 coating on the surface of Mn-Cd-S. The resultant Mn-Cd-S@amorphpus-Ni3S2 catalyst presents good stability and a high photocatalytic H-2 evolution rate of 12,069.27 mu molh(-1) g(-1). Besides, both Mn-Cd-S and Mn-CdS@amorphpus-Ni3S2 show good OER property with overpotential of 333 mV. Mn-Cd-S@amorphpus-Ni3S2 shows more favorable kinetics than that of Mn-Cd-S for OER. Moreover, the mechanism of the enhanced photo/electrocatalytic performance is investigated in detail. This work provides references for developing the catalysts with both photocatalytic and electrocatalytic properties.