Spontaneous hyperacute subdural hematoma is a rare entity. The sequential change in density of subdural hematomas (SDHs) on computerized tomography (CT) is crucial to understand the pathogenesis and evolution of SDHs. Definitive diagnosis of spontaneous or non-traumatic intracranial hematoma of arterial etiology may also be shown on digital cerebral angiography however CT scan is usually more efficient and practical not to delay the operative intervention. The appearance of extraaxial hematoma is typical and hypodense signals within the hyperdense hematoma content may signify active arterial bleeding. Here, we report a 72-year-old man who presented with sudden loss of consciousness and hyperacute subdural hematoma included in swirl sign on his cranial CT scan.