The incidence rate of spontaneous remission of malignant cancer is very low. Reports on spontaneous remission in advanced prostate cancer are extremely limited. Our patient was treated with androgen deprivation therapy, local radiotherapy, and surgical castration at the initial diagnosis. Approximately nine years after treatment, he experienced a rise in serum prostate-specific antigen level and relapse of obturator lymph node adenopathy. Initially, androgen deprivation therapy was reinitiated, which resulted in castration-resistant prostate cancer. Although androgen deprivation therapy was discontinued, spontaneous remission of recurrent lymph node and spontaneous reduction in serum prostate-specific antigen level was seen. There was no sign of radiological recurrence for over eight years without prostate cancer treatment.