The investigation of earth-abundant, durable, and efficient bifunctional electrocatalysts for overall water splitting was critical to future renewable energy systems. Herein, flower-like Mn-doped Cu7.2S4@NiS2@NiS was successfully assembled on 3D nickel foam (NF) substrate via a facile two-step hydrothermal-sulfuration method (denote as flower-like Mn-2-CNN/NF). Benefited from unique 3D configuration with firm contact between nanoflowers and Ni foam, flower-like Mn-2-CNN/NF electrode demonstrated a low overpotential of 252 mV to achieve a current density of 50 mA cm(-2) and 24 h-long stability toward oxygen evolution reaction (OER) in 1 M KOH. For hydrogen evolution reaction (HER), a stable current density of 10 mA cm(-2) at only an overpotential of 87 mV and a low Tafel slope of 43.7 mV dec(-1) were observed. Furthermore, when assembled as electrolyzers on both cathode and anode for stable water splitting, a low cell voltage of 1.514 V was needed for flower-like Mn-2-CNN/NF to afford the current density of 10 mA cm(-2) and distinguished durability for over 46 h was observed, which presented a wide range of possibilities for the development of earth-abundant and high efficient electrode pairs.