Cancer can cause sexual adverse effects by direct and indirect pathways. It can involve sexual organs, indirectly affect body image, or cause fatigue or depression with subsequent effects on libido. Erectile dysfunction (ED), the inability to obtain or maintain an erection firm enough for sexual intercourse, can also result from adverse effects of cancer treatment, such as fatigue, pain, or anxiety about therapy. In addition, depressed feelings about having cancer can affect sexuality, causing a range of signs and symptoms that can lead to ED. Chemotherapy, hormone therapy, surgery, and radiation can all cause sexual adverse effects. Additional factors that play a role include patient age and degree of ED before starting cancer treatment. In this article, we discuss how chemotherapy, hormone therapy, surgery, and radiation affect erectile function as well as possible treatment options for ED.