Male infertility and fertility preservation in cancer patients have been frequently discussed. Cancer is not rare in men, especially young men, and it has several adverse effects on the reproductive organs, such as the testicles and other endocrine organs, resulting in infertility or subfertility. As cancer treatments improve, cancer survivors are steadily increasing in number and fertility preservation in young men is becoming another major concern, separate from the treatment of cancer itself. Simultaneously, the advance of assisted reproductive techniques (ART) has led to new possibilities for the prevention and treatment of infertility. This report reviews 1) the impact of cancer on fertility, 2) infertility after cancer therapy, such as surgery, chemotherapy, and/or radiation therapy, and 3) fertility preservation.