From January 2007 to April 2012, we performed 2427 surgical clippings for unruptured intracranial aneurysms (UIAs). Among these patients, two cases showed symptomatic and angiographic cerebral vasospasm in the delayed post-operative period without a complicated event. Additionally, we reviewed four cases of delayed cerebral vasospasms following uncomplicated operations that were consistent with our inclusion criteria in the previous literature. The pathogenesis and characteristics of these rare occurrences are reviewed from our two cases and previous literature. For clipping of UIAs, it should be kept mind that neurological symptoms are caused by delayed cerebral vasospasm, and careful observation with proper conservative treatment are necessary to ensure favorable outcomes.