Our group published a review on the roles of oxygen vacancies in electrocatalytic oxygen evolution reaction (OER). The efficiency of many rechargeable energy storage technologies and hydrogen production from water splitting is limited by the OER due to its sluggish kinetics. Oxygen vacancy engineering is an effective approach to tune the electronic structure of electrocatalysts and the surface absorption/desorption of reactants, thus affecting OER activity. To make the oxygen vacancy effect clear, the recent development of manipulating the oxygen vacancies in electrocatalysts for enhancing OER performance is reviewed and the proposed mechanisms for the enhanced performance are discussed in detail. In addition, various approaches for generating oxygen vacancies in electrocatalysts and characterization methods for oxygen vacancies are also summarized. Furthermore, the challenges in designing high-efficient OER electrocatalysts and outlooks in understanding the oxygen vacancy-activity relationship are discussed. This work has been published in Nano Energy, 2020, 73, 104761.