Although the survival rate of hematologic malignancies in young patients is very high, cytotoxic therapies such as chemotherapy and total body irradiation therapy can significantly reduce a patient's reproductive capacity and cause irreversible infertility. Early ovarian failure also commonly occurs following additional cancer treatment, bone marrow transplantation, or autologous transplantation. Because the risk of early ovarian failure depends on the patient's circumstances, patients with a hematologic malignancy must consult health professionals regarding fertility preservation before undergoing treatments that can potentially damage their ovaries. While it is widely known that early menopause commonly occurs following breast cancer treatment, there is a lack of reliable study results regarding fertility preservation during hematologic malignancy treatment. Therefore, an in-depth discussion between patients and health professionals about the pros and cons of the various options for fertility preservation is necessary. In this study, we review germ cell toxicity, which occurs during the treatment of hematologic malignancies, and propose guidelines for fertility preservation in younger patients with hematologic malignancies.