The diagnosis of cancer in men or women leads to prompt evaluation of the extent of the cancer, its treatment, and subsequent prognosis. However, relatively little emphasis is placed on fertility following the completion of therapy. As the effectiveness of cancer treatment has improved, men can enjoy a longer life that is free of cancer. However, chemotherapeutic regimens alone or in combination with radiation therapy frequently result in azoospermia or infertility. This paper reviews available methods to maintain male fertility in patients undergoing chemotherapy or radiation therapy. Certain chemotherapeutic agents that are less likely to cause azoospermia may be incorporated into potentially curative therapies. Hormonal suppression applied early (prior to) and during chemotherapy may protect future male fertility. Alternatively, cryopreservation of sperm enables men to reproduce in the future with the assistance of in vitro fertilization with intracytoplasmic sperm injection. Therefore, oncologists need to discuss male fertility preservation before initiating cancer treatment in reproductive-aged men. The emphasis for future cancer treatment and its research regarding male fertility preservation needs further attention.