Infratentorial subdural empyema is a life-threatening rare complication of bacterial meningitis. Infratentorial subdural empyemas constitute only a small portion of all cases with intracranial infectious diseases. We present a 15-year-old boy with infratentorial subdural empyema. Empyema was diagnosed with serial follow-up computed tomography and magnetic resonance imaging while he was being treated for bacterial meningitis secondary to neglected mastoiditis. The patient was successfully treated with emergent surgery and appropriate antibiotics. Empyema should be considered in patients with suspected or proven bacterial menengitis and associated ear nose throat infection with neurological signs that suggest a posterior fossa lesion.