Chronic subdural hematoma (CSDH) is a common pathology in the elderly but very rare in young adults. When CSDH occurs in this age group, severe head injury or some promotive factors are usually present. This article reports the case of a 29-year-old female presented at our Emergency Department with a few days' history of progressive frontal headache. Computed tomography scan of the head showed a right frontal CSDH. Only a decreased level of consciousness without focal deficits was present at clinical examination and her medical history was negative for trauma or promotive factors. Blood count showed a mild sideropenic anemia while coagulation tests were normal. No vascular malformations were shown at digital subtraction angiography. The patient underwent craniotomic evacuation. After surgery, the patient showed a full neurological recovery. Spontaneous CSDH in young adults is very rare. In the worldwide literature, many cases of non-traumatic CSDH are reported, but a promotive factor is generally present. We described a case of spontaneous CSDH, whose etiology remains unknown.