Herniation of the lumbar disc is a common cause of low back pain. Conservative management with physiotherapy, such as lumbar spine traction, is usually effective. Although a schwannoma of the lumbar spine is relatively uncommon, the clinical manifestations are similar to those of lumbar disc herniation, making the diagnosis difficult. This case report describes a 51-year-old male who had suffered from low back pain for 3 years and who was diagnosed with L2/L3 lumbar disc herniation. The low back pain was well-controlled by conservative treatment and the symptoms improved progressively. Two months prior to our evaluation, however, the symptoms worsened acutely, and were accompanied by the onset of symptoms of cauda equina syndrome. A small tumor at the site of the L2/L3 disc herniation, observed incidentally during magnetic resonance imaging, was responsible for the symptoms of spinal stenosis at the lumbar region. The patient underwent laminectomy, tumor resection, and discectomy with near-complete resolution of symptoms. In patients with lumbar disc herniation that improves with conservative treatment, the recurrence of symptoms should prompt a thorough review of the medical history, physical examination, and imaging studies to establish the diagnosis and prevent delay in treatment.