The primary cause of nail tumors, as with other skin cancers, is exposure to ultraviolet (UV) radiation. Nails, like skin, should be protected from the harmful effects of the sun, and broad-spectrum sunscreens should also be applied to them. Individuals with sensitive skin are especially advised to be more careful in this regard.

Other potential causes of nail tumors include chronic traumas, chemical exposures, radiation therapies, cancer types that suppress the immune system such as lymphoma and leukemia, immunosuppressive drugs like chemotherapy, and infections such as HIV/AIDS. The possibility of cancer should also be considered in any chronic wound or bleeding.