The Life-sustaining Treatment Decisions Act has became enforced in 2018. Patients' decision-making on life-sustaining treatments can change according to their health status and situations and thus should be understood as the process requiring continuous care. Therefore, it is necessary to build a support system to help patients' decision-making at end-of-life care including life-sustaining treatments. Nurses provide continuous care at the bedside and play a significant role in supporting patients' and their families' decision-making about end-of-life care. Based on reviewing literature and the enforcing process of the Life-sustaining Treatment Decisions Act, this paper described nurses' nursing care activities to support decision-making on life-sustaining treatments. The nursing care activities are 'empathetic support for the decision-making,' 'respect for patients and families as agents for the decision-making,' and 'support for the decision-making as a counselor.' It can emphasize the importance of a nurse's role as a support system for patients’ and their families' decision-making about end-of-life care.