Thunderclap headache is an acute and severe headache and is often the first sign of a life-threatening neurovascular disorder. The case of a 44-year-old man is described who presented with a thunderclap headache as the only clinical symptom. The clinical examination did not reveal any other focal deficits or signs of motor or sensory failures. Routine blood tests, cerebral CT as well as cerebrospinal fluid analysis showed no pathological results. A cerebral MRI to exclude a symptomatic thunderclap headache revealed a right cerebellar infarction. This case expands the differential diagnosis of thunderclap headache and reinforces the need for magnetic resonance imaging in the evaluation of such patients, even when neurological examination, cerebral CT, and cerebrospinal fluid analysis are normal.