We report an early-onset post-traumatic hemifacial spasm and discuss possible aetiology. A 20-year-old man was admitted to our hospital for observation because of an injury to the right frontotemporal region, resulting in drowsiness. On the second day in hospital, he developed peripheral paresis of the facial nerve on the right, followed by hemifacial spasm on the same side. He improved after corticosteroid treatment, and was discharged one week later almost completely recovered. The neuroradiology and clinical response suggest that the patient's hemifacial spasm was due to hyperexcitability of the facial nerve nucleus induced by a haematoma in the lower central pons.