The precise mechanism involved in DIC and delayed traumatic subarachnoid hemorrhage (DT-SAH) remains unclear in multiple-trauma patients. Hereby, we describe a polytraumatized patient with DIC who died due to DT-SAH. A 75-year-old female patient was admitted to our Emergency Department complaining of abdominal pain and drowsiness after a pedestrian accident. Her initial brain computerized tomography (CT) finding was negative for intracranial injury. However, her abdominal CT scan revealed a collection of retroperitoneal hematomas from internal iliac artery bleeding after a compressive pelvic fracture. This event eventually resulted in shock and DIC. An immediate angiographic embolization of the bleeding artery was performed along with transfusion and anti-thrombin III. Her vital signs were stabilized without neurological change. Fourteen hours after admission, she suddenly became comatose, and her follow-up brain CT scan revealed a dense DT-SAH along the basal cisterns with acute hydrocephalus. This event rapidly prompted brain CT angiography and digital subtraction angiography, which both confirmed the absence of any cerebrovascular abnormality. Despite emergency extraventricular drainage to reverse the hydrocephalus, the patient died three days after the trauma. This paper presents an unusual case of DT-SAH in a polytraumatized patient with DIC.