The development of oxygen evolution reaction (OER) catalysts with high activity and high stability through convenient and economical methods is greatly important for the promotion of hydrogen energy based on electrolysis technology. Herein, by using an unconventional high electrodeposition potential, novel petal-like clusters constructed by cross-linking ultrathin nickel hydroxide nanosheets were controllably synthesized on nickel foam (or copper foam or carbon cloth) and the effect of electrodeposition conditions on their OER performance was carefully explored. Due to the abundant catalytically active sites, promoting electron conduction/mass transmission from the specific micro–nano structure, as well as the ultrasmall thickness of ∼3.0 nm, the optimized α-Ni­(OH)2/NF self-supporting electrode exhibits excellent electrocatalytic performance for OER, merely requiring low overpotentials of 192 and 240 mV to yield current densities of 10 and 100 mA cm–2 in 1.0 M KOH, respectively, which surpassed those of all of the reported nickel hydroxide/oxides and the benchmark RuO2. Moreover, α-Ni­(OH)2/NF can drive the high-current density (500–1000 mA cm–2) OER at low overpotentials, meeting the requirements of potential industrial applications.