A 32-year-old man visited our hospital due to urinary retention. Prostate-specific antigen was 13.7 ng/mL. Imaging examinations showed a large prostatic tumor and lung and internal iliac lymph node metastases. Transrectal biopsy confirmed embryonal rhabdomyosarcoma of the prostate classified as cT2bN1M1 (stage IV) by the International Rhabdomyosarcoma Study (IRS) Group staging system. Systemic chemotherapy was started according to the IRS III regimen 36, which consisted of 16 weeks of induction chemotherapy with radiation. After 20 weeks, magnetic resonance imaging showed the disappearance of metastases, and the prostate tumor shrunk markedly. Moreover, prostatic re-biopsy showed no viable tumor cells. Maintenance chemotherapy, excluding vincristine because of severe peripheral nerve disorder, was performed for 2 years. There has been no recurrence for 49 months after the termination of maintenance chemotherapy. To the best of our knowledge, this is the longest surviving case of adult-onset metastatic rhabdomyosarcoma of the prostate reported in the literature.