Mandatory reporting is the obligation in certain countries for health-care personnel and other professionals to report known or suspected cases of sexual or gender-based violence to designated public authorities, notably to law enforcement agencies. It includes providing identifying information, without requiring the consent of the victim/survivor. In some contexts, the victim/survivor is required to report as a precondition for accessing care. States introduce mandatory reporting to respond to their due diligence obligations to investigate, prosecute and punish violent crimes, to prevent them from occurring, and to better protect victims/survivors. The British Red Cross and the International Committee of the Red Cross (ICRC) conducted research in health care settings in four countries affected by armed conflict or other emergencies. The research focussed on the situation for adult victims/survivors. It revealed that mandatory reporting of sexual violence in these contexts can obstruct access to health care for the victims/survivors of these crimes and may expose them to increased risk of secondary violence and harm. This paper analyses and produces evidence of the various challenges of providing health care where mandatory reporting of sexual violence exists and details the negative humanitarian impacts in armed conflict and other emergencies. The report makes recommendations to States that have mandatory reporting regimes, as well as to donors, health-care providers and the Red Cross and Red Crescent Movement, on how to respond to these dilemmas and better protect the health, safety and well-being of survivors.