Cerebral ischemia is a severe condition, often resulting from interference with blood supply to the CNS. The results of oxygen and glucose deprivation (OGD) lead to ischemic cell death. The neuronal large conductance, voltage and Ca2+-activated (BK) K+ channel is thought to play a key role in negative feedback control of intracellular Ca2+ concentration thus protecting neuronal cells from excess Ca2+ influx through voltage-dependent Ca2+ channels during pathophysiological environments. The minimally invasive endovascular filament model was applied to induce transient middle cerebral artery occlusion (MCAO) in BK channel-deficient (BK-/-) mice. BK-/- mice showed increased infarct volume and post-ischemia mortality, and more severe neurological deficit compared with wild-type (WT) mice. There were no gross anatomy differences in the vascular pattern of the cerebral circulation. Cerebral blood flow after anesthesia, during transient MCAO and during reperfusion was not significantly different between genotypes. BK-/- cultures showed enhanced cell death in CA1 after OGD than WT cultures. Our results indicate that neuronal BK channels are important for protection against ischemic brain damage. Thus, BK channels may be considered as putative target for acute therapeutic intervention against stroke.