Bifunctional electrocatalysts, which are active both for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), can increase the efficiency of overall water splitting, which is considered an attractive technology for hydrogen production. In this study, we report NiCo-LDH ultrathin nanosheets grown on nickel foam as a bifunctional electrocatalyst for overall water splitting. When used as OER and HER electrodes, NiCo-LDH/NF demonstrated excellent water splitting performance, achieving a current density of 10 mA cm-2 at 1.66 V. Thus, the synthesis of hierarchical 3D porous structure composed of 2D ultrathin nanosheets in NiCo-LDH/NF demonstrated the significance of structural features for achieving a high electrocatalytic activity in overall water splitting.