We report here a rare case of small cell lung cancer (SCLC) accompanied by a partial spontaneous regression with a progression of paraneoplastic sensory neuropathy (PSN). A 55-year-old woman was admitted to our hospital with dry cough and progressive numbness in the distal extremities over 1 month. She was diagnosed as small cell lung cancer associated with paraneoplastic sensory neuropathy. About 1 month later, partial spontaneous regression of tumor with a progression of paraneoplastic sensory neuropathy was observed. A complete response was achieved through chemotherapy and concurrent radiotherapy. As the tumor size decreased, her neurological symptoms improved. A short interval between onset of PSN and the start of therapy may be essential for successful treatment for not only SCLC but also PSN.