Spontaneous remission (SR) of cancer, especially of lung tumor, is a rare biological event. Only seven cases in which small cell lung cancer (SCLC) regressed spontaneously had been previously reported. We report here a rare case of complete SR of SCLC in an 86-year-old man. Paraneoplastic sensory neuronopathy (PSN) is a rare syndrome, which is associated with malignancy such as SCLC and starts with dysesthetic pain and numbness in the distal extremities, then spreading all four limbs and trunk causing severe sensory ataxia. In the previous reports, SR of SCLC is suggested to result from surgical trauma or PSN, which may be able to enhance anti-tumoral immunity. Our report is the case of SR of SCLC, without any therapies nor any invasive examinations. Although the reason of SR of SCLC in the present case is unknown, PSN could be one of the diagnosis by exclusion.