Constructing efficient bifunctional electrocatalysts for both cathode and anode is of great importance for obtaining green hydrogen by water splitting. Herein, sulfuration of hierarchical Mn-doped NiCo LDH heterostructures (Mn–NiCoS2/NF) is constructed as a bifunctional electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) via a facile hydrothermal-annealing strategy. Mn–NiCoS2/NF shows an overpotential of 310 mV at 50 mA cm−2 for OER and 100 mV at 10 mA cm−2 for HER in 1.0 M KOH. Moreover, only 1.496 V@10 mA cm−2 is required for overall water splitting by using Mn–NiCoS2/NF as catalyst dual electrodes in a two-electrode system. The excellent performance of Mn–NiCoS2/NF should be attributed to the ameliorative energy barriers of adsorption/desorption for HO−/H2O through the modification of electronic structure of NiCo basal plane by Mn-doping and the acceleration of water dissociation steps via rich delocalized electron inside sulfur vacancies. The construction of hierarchical Mn–NiCoS2/NF heterostructures provides new prospects and visions into developing efficient-advanced electrocatalysts for overall water splitting.