Purpose: To investigate the clinical outcomes of percutaneous transforaminal endoscopic discectomy assisted with selective nerve root block for treating radicular pain with diagnostic uncertainty in the elderly. Methods: A total number of 36 elderly patients were included in the study. Clinical outcomes collected for analysis include operative time, hospital stay time, Visual Analog Scale, and Oswestry Disability Index before and after the surgery, the global outcome based on the Macnab outcome criteria. Results: Seventeen males and nineteen females with a mean age of 73.72 +/- 7.15 were included in this study. Radicular pain was the main complaint of all the patients with the least symptom duration of two months. Radiological findings showed that 80.6% of the patients with multilevel disc herniation, 16.7% received lumbar fusion surgery before, and 8.3% with degenerative scoliosis. Besides, 69.4% of the patients have at least one comorbidity. 85.4% of the patients showed a positive response to selective nerve root block, and 91.6% of the patients reported a favorable outcome at the last follow-up. The mean value of pre-operative leg pain was 7.56 +/- 0.74 and dramatically decreased after surgery (2.47 +/- 0.81, P < 0.001). Besides, the mean value of Oswestry Disability Index decreased from 43.03 +/- 4.43 to 5.92 +/- 5.24 (P < 0.001) one year after the surgery. Conclusion: Multilevel degeneration of the lumbar spine is common in elderly patients. Identifying the responsible segment and decompressing the nerve root through minimally invasive surgery can provide a satisfactory clinical outcome for those with radicular pain as their primary complaint. And selective nerve root block is a reliable diagnostic tool for those with an ambiguous diagnosis.