Spontaneous spinal epidural hematoma (SSEH) is a rare condition, and its etiology remains unclear. Spinal venous wall instability due to intravenous pressure changes and the resultant venous rupture seem to be the underlying pathophysiological mechanisms. Here, the authors report a case of posterior SSEH at the C3-5 level causing mild left hemiparesis in a previously healthy 56-year-old woman. Angiography performed at the time of admission showed left internal jugular vein (IJV) thrombotic occlusion and dilation of the surrounding venous plexus, strongly suggesting that these pathologies caused the SSEH. Furthermore, immediate MR imaging suggested severely impaired blood flow in the left IJV. The hematoma soon resolved after spontaneous IJV thrombolysis. The authors' radiological observations imply that idiopathic IJV thrombosis may cause cervical SSEH.