To identify and appraise evidence about ethical concerns regarding conducting medical research with end-of-life patients. A best-fit framework synthesis of the literature regarding ethical issues in research involving adult patients at the end of life was conducted. Five databases were searched (Cumulative Index to Nursing and Allied Health Literature, Web of Science, Embase, MEDLINE, and PsychINFO) between January 2000-August 2019. Data were synthesized and categorized according to the moral positions described by Foster. In all, 18 papers that met the inclusion criteria were included in this review. These papers provided rich knowledge not only about various ethical objections to researching the end of life but also about the social, moral, and clinical requirements to perform rigorous studies on clinical interventions in this field. Research on people at end of life is not an unsolvable ethical dilemma between providing the best possible care and enhancing new therapies. It is important to find a balance between the moral duties of providing care and achieving research outcomes that are rigorous and meaningful for service users. Research ethics committees can be challenged by the evaluation of human research. This review provides up-to-date evidence on key challenges and ethical considerations about researching with end-of-life patients. This study is a review of relevant evidence and key ethical challenges and issues around palliative and end-of-life research. Our findings provided important recommendations for clinicians, research, and ethics committee members when evaluating clinical research with people at their end of life.