Subdural empyema is a life-threatening infection that may complicate acute sinusitis. The authors report the case of a previously healthy 10 year-old girl who presented with subdural empyema due to Gemella morbillorum after an untreated maxillary, ethmoidal and esphenoidal sinusitis. Despite immediate drainage of the empyema and underlying primary infection and treatment with broad spectrum antibiotics, she later developed frontal cerebritis and refractory intracranial hypertension, needing urgent decompressive craniectomy. She recovered gradually, maintaining to date slight right hemyparesis and aphasia. Even though it is considered a low virulence organism, G. morbillorum has been increasingly described in central nervous system infection. In this case, the prompt institution of broad spectrum antibiotics and surgical drainage, as well as the agressive treatment of complications, including decompressive craniectomy, were crucial to the patient's recovery.