Patients with cancer often experience insomnia. Nightmares are also a strong factor that interferes with the maintenance of comfortable and satisfying sleep. However, the prevalence and standard treatment of nightmares in patients with cancer have not been established yet. We aimed to treat insomnia and nightmares with trazodone. From 2008 to 2011, trazodone was prescribed to 30 patients with cancer who reported experiencing insomnia with or without nightmares to the palliative care team in Osaka University Hospital. Effective treatment was seen in 15 patients (50%). Four patients with cancer reported having severe nightmares and 2 patients had beneficial effects, with frightening dreams transformed into acceptable ones. Trazodone may be an effective drug for the treatment of insomnia and nightmares in patients with advanced cancer.