The authors report a rare case of a patient with a left-sided T-5 radiculomedullary artery pseudoaneurysm who presented with spinal subarachnoid hemorrhage (SAH). The patient, a 71-year-old woman, was hospitalized for progressive paraplegia and sensory loss with bladder and rectal dysfunction. Computerized tomography scanning revealed an SAH at the posterior fossa. Spinal T2-weighted magnetic resonance imaging demonstrated SAH and an inhomogeneous and slightly low signal intensity mass at T4-5. Spinal angiography revealed a tiny masslike staining without arteriovenous shunting. The resected specimen, which caused the spinal SAH, was diagnosed as a pseudoaneurysm based on operative and pathological findings.