Religion and spirituality have long been considered important social determinants of human health, and there exists an extensive body of research to support such. End-of-life (EOL) may raise complex questions for individuals about religious and spiritual (R/S) values guiding advance care planning (ACP) and EOL care decisions, including the provision of spiritual care. This commentary will review the history and current national trends of ACP activities for EOL, principally within the United States. It will describe the relationship of religious variables and the attributes of selected research instruments used to study religious variables on ACP and EOL preferences. The review also summarizes unique ACP challenges for patients with neurocognitive disorders and severe mental illness. Findings disclose that higher levels of religiosity, reliance on religious coping, conservative faith traditions, and "belief in God's control over life's length and divine intervention have lower levels of ACP and more intensive EOL care preferences, although the provision of spiritual spiritual care at EOL mitigates intensive EOL care. Based upon the curated evidence, we propose an epistemological justification to consider "faith" as a separately defined religious variable in future ACP and EOL research. This review is relevant to geriatric psychiatrists and gerontological health care professionals, as they may be part of multidisciplinary palliative care teams; provide longitudinal care to patients with neurocognitive disorders and severe mental illness; and may provide diagnostic, emotional, and therapeutic services for patients and families who may struggle with EOL care decisions.