Progesterone (P4) exerts long-term neuroprotective effects in animal models of stroke, and P4 receptors play a crucial role in this neuroprotection. However, it currently remains unclear whether the activation of P4 receptors alone is sufficient to exert long-term neuroprotection because P4 exhibits other steroidogenic and GABAergic activities via several of its metabolites. Nestorone is a potent selective P4 receptor agonist without other steroidogenic and GABAergic activities. Therefore, we examined the effects of nestorone in adult male rats subjected to transient middle cerebral artery occlusion (MCAO). The dose-response relationship of nestorone showed that the 6-h post-ischemic administration of 10 μg/kg nestorone resulted in greater reductions in infarct sizes 48 h after MCAO than the other two doses tested (5 and 80 μg/kg), and this dose of nestorone significantly decreased astrocyte activation in the peri-infarct cortical region. Moreover, 10 μg/kg nestorone significantly prevented functional impairments on the 28th and 29th days and slightly reduced infarct size on the 30th day after MCAO. The present results suggest that the activation of P4 receptors alone is sufficient to exert neuroprotection against transient cerebral ischemia in adult male rats; therefore, nestorone is a promising agent in post-stroke treatment due to its potent progestational effects without other steroid-related activities.