Recent advances in cancer treatment have markedly improved survival outcomes, increasing the importance of long-term quality of life issues, including male gonadal function. Cancer-related gonadal dysfunction results from the combined effects of the malignancy itself and anticancer therapies and primarily manifests as impaired spermatogenesis, although Leydig cell dysfunction may also contribute to long-term endocrine sequelae. Conventional treatments, including radiotherapy, surgery, and cytotoxic chemotherapy, have well-established gonadotoxic effects, whereas the long-term reproductive and endocrine consequences of newer anticancer therapies, such as molecular targeted agents and immune checkpoint inhibitors, remain incompletely understood. Although recovery of spermatogenesis is possible in some patients, persistent azoospermia and compensated or overt hypogonadism may develop after treatment. Sperm cryopreservation before gonadotoxic therapy remains the cornerstone of fertility preservation and should be considered for all eligible patients. In selected cancer survivors with persistent post-treatment azoospermia, microdissection testicular sperm extraction may provide an opportunity for biological fatherhood. In addition, increasing evidence suggests that long-term endocrine follow-up should address not only overt testosterone deficiency but also compensated Leydig cell dysfunction. As oncological outcomes continue to improve, clinicians should strive not only to cure cancer but also to preserve the long-term reproductive and endocrine health of cancer survivors through individualized treatment strategies and survivorship care.