A 37-year-old woman with congenital afibrinogenemia presented with chronic subdural hematoma (CSDH) manifesting as severe headache, nausea, and somnolence after a minor head trauma. Brain computed tomography scans showed a right subdural hematoma associated with midline shift. Laboratory studies showed prolongation of prothrombin time, activated partial thromboplastin time, and undetectably low level of fibrinogen. Until the present episode, she had received plasma-derived fibrinogen concentrate around menstruation and pregnancy. She had also suffered from spinal cord infarction due to vertebral artery occlusion. Burr-hole evacuation and drainage of CSDH was successfully performed using fibrinogen concentrate. The development of CSDH with afibrinogenemia is very rare. Although the past repeated administrations of fibrinogen concentrate were suspected to generate CSDH, paradoxical thrombotic complications caused by upregulation of prothrombin activation, thrombin generation, and growth factors released from platelets might be related to the development of CSDH with congenital afibrinogenemia.