The exploration of efficient electrocatalysts is the central issue for boosting the overall efficiency of water splitting. Herein, pertinently creating active sites and improving conductivity for metal–organic frameworks (MOFs) is proposed to tailor electrocatalytic properties for overall water splitting. An Ni(II)‐MOF nanosheet array is presented as an ideal material model and a facile alkali‐etched strategy is developed to break its NiO bonds accompanied with the introduction of extra‐framework K cations, which contribute to creating highly active open metal sites and largely improving the electrical conductivity. As a result, the assembled defect‐Ni‐MOF||defect‐Ni‐MOF electrolyte cell delivers a lower and stable voltage of 1.50 V at 10 mA cm−2 in alkaline medium for overall water splitting, comparable to the combination of iridium and platinum as benchmark catalysts. The introduction of defects into metal–organic framework (MOF) by alkali‐etching treatment to create rich active sites and tailor electrical conductivity is proposed. The resultant defect‐rich Ni(II)‐MOF nanosheet array exhibits excellent electrocatalytic overall water splitting performance, comparable to the noble metal‐based benchmark catalysts.