Requests for a second medical opinion (SMO) by patients or substitute decision-makers (SDMs) can arise during end-of-life disputes in critical care. Such disagreements between patients or SDMs1 and physicians often pertain to specific elements of the decision-making process related to withholding or withdrawing of life-sustaining treatments. When these disputes occur in the critical care setting in Canada, practicalities and policy barriers prevent an SDM from obtaining an SMO without support from healthcare providers; moreover, in a majority of these cases the SDM will require the facilitation of a physician who is often the same individual with whom they are in conflict. Institutional and a national society's policy statements propose SMOs as an important component of a conflict resolution process for end-of-life disputes (Bosslet et al. 2015; Singer et al. 2001). However, these policies do not provide specific guidance to physicians on how to fairly consider SMO requests. Given the vulnerable position of patients and their SDMs in the critical care context and in order to promote fairness, physicians should apply consistent standards in deciding whether to facilitate a request for an SMO. To guide physicians' decision-making and inform future policy development, we propose three ethical principles for considering SDM requests for an SMO in critical care at the end of life.