High efficiency, low cost and stable electrocatalysts are very important for large scale applications of water splitting. Therefore, we report a core–shell nanostructure Co3O4@NiCo LDH catalyst with Co3O4 nanowires as the core and NiCo LDH nanosheets as the shell, which has better electrocatalytic performance in alkaline solution compared with pure Co3O4 and NiCo LDH. The as-prepared Co3O4@NiCo LDH catalyst displays excellent activity for the OER with only overpotential of 279 mV to drive the current density of 15 mA cm−2. In addition, it also exhibits prominent HER activity, only requiring a small overpotential of 113 mV at 10 mA cm−2. The synergistic effect from Co3O4 and NiCo LDH promotes the catalytic performance of electrocatalysts in overall water splitting systems, only requiring 1.66 V to reach the current density of 10 mA cm−2 in a two-electrode alkaline electrolyzer. At the same time, the catalytic performance of the electrode has no obvious change after long time working, demonstrating its outstanding stability.