A 60-year-old female presented with sudden onset of severe headache and back pain, followed by nausea. The initial head computed tomography (CT) scan revealed posterior fossa subarachnoid hemorrhage (SAH). Spinal T(2)-weighted magnetic resonance imaging demonstrated SAH, and a homogeneous and slightly low signal intensity mass at T11. Spinal angiography in the early arterial phase revealed a small pearl and string-like aneurysm of the proximal radiculomedullary artery on the left side at the T12 level. Forty days after the onset of SAH, CT angiography demonstrated complete occlusion of the dissecting aneurysm and the preserved anterior spinal artery. The present case of ruptured dissecting aneurysm of the radiculomedullary branch of the artery of Adamkiewicz with SAH underwent subsequent spontaneous occlusion, indicating that the wait-and-see strategy may be justified and will provide adequate treatment.