Low efficiency, short lifetimes, and limited kinds of catalysts are still three fundamental shortcomings that have plagued electrochemical water splitting. Herein, we rationally synthesized a cost-effective Co 3 S 4 @MoS 2 hetero-structured catalyst that has proven to be a highly active and stable bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline environment. The heterostructure was obtained via a first hydrothermal approach to obtain hollow Co 3 S 4 nanoboxes based on the ionic exchange reaction between Fe(CN) 6 3− of Co-Fe Prussian blue analogue (PBA) and S 2− at 120 °C, and the subsequent in situ growth of MoS 2 nanosheets on the surface of Co 3 S 4 nanoboxes at an elevated temperature of 200 °C. The synergistic effects between the active and stable HER catalyst of MoS 2 and the efficient OER catalyst of Co 3 S 4 , as well as the morphological superiority of hollow and core-shell structures, endow Co 3 S 4 @MoS 2 with remarkable electrocatalytic performance and robust durability toward overall water splitting. As a result, the designed non-noble electrocatalyst of Co 3 S 4 @MoS 2 exhibits a low overpotential of 280 mV for OER and 136 mV for HER at a current density of 10 mA cm −2 in an alkaline solution. Meanwhile, a low cell voltage of 1.58 V is achieved by using the heterostructure as both anode and cathode catalysts. This work paves the way to the design and construction of other prominent electrocatalysts for overall water splitting.