The process of shared decision making (SDM) is an ethical imperative in the physician-patient relationship, especially in the emergency department (ED), where SDM can present unique challenges because patients and emergency physicians often have no established relationship and decisions about diagnosis, treatment, and disposition are time dependent. SDM should be guided by the ethical principles of autonomy, beneficence, nonmaleficence, and justice and the related principle of stewardship of finite resources. The objective of this article is to outline the ethical considerations of SDM in the ED in the context of diagnostic evaluations, therapeutic interventions, disposition decisions, and conflict resolution and to explore strategies for reaching decision consensus. Several cases are presented to highlight the ethical principles in SDM in the ED. SDM is an important approach to diagnostic testing in the ED. Achieving agreement regarding diagnostic evaluations requires a balance of respect for patient autonomy and stewardship of resources. SDM regarding ED therapeutic interventions is an important component of the balance of respect for patient autonomy and beneficence. While respecting patient autonomy, emergency physicians also recognize the importance of the application of professional judgment to achieve the best possible outcome for patients. SDM as an ethical imperative in the context of ED disposition is especially important because of the frequent ambiguity of equipoise in these situations. Unique clinical situations such as pediatric patients or patients who lack decisional capacity merit special consideration.