Abstract Background Signing advance directives (ADs) ensures that terminally ill patients receive end-of-life care, according to their wishes, thereby promoting human dignity and sparing them from unnecessary suffering. Despite the enactment of the Hospice Palliative Care Act in Taiwan in 2000, the completion rates of ADs have been found to be low among patients with chronic illness conditions. To date, limited existing research is available regarding the factors associated with AD completion in terminally ill patients in Taiwan. To explore signed AD characteristics, compare differences in signing ADs between patients with and without cancer, and examine the factors associated with signing ADs in terminally ill patients. Methods A nationwide study was conducted using data collected via a retrospective review of medical death records from 18 randomly selected hospitals in the northern, central, and southern parts of Taiwan. We collected 200 records, including both cancer and non-cancer-related deaths, from each hospital. Univariate and multivariate logistics regressions were conducted to examine factors associated with signing advance directives among all patients- with and without cancer. Results Among the 3004 reviewed medical records, 79% had signed ADs, with most (95%) being signed by patients’ caregivers. A higher education level (OR = 1.52, 95% CI = 1.10, 2.08, p = 0.010); cancer diagnosis (OR = 2.37, 95% CI = 1.79, 3.16, p