Laudable aspects of open science are known, accepted, and documented. Ethical limits of open science exist, with security frequently mentioned. Disaster diplomacy, which investigates how and why disaster-related activities do and do not influence conflict and cooperation, exemplifies the need for balance among: -Research ethics: Some investigations and material can be counterproductive to avoiding disasters and to reaching peace. -Open science: Publicly communicating data and scientific analyses can be used to augment disaster risk and conflict. -Perceived security: International collaboration and positive action are at times impeded by keeping confidential data on disasters, including conflict. Accepting practical, operational limits for ethical open science, whether or not securitisation is supported, can improve the science and impact value of disaster diplomacy research, internationally and locally. These limits are espoused by established ethoses of ‘responsible open science’ and ‘as open as possible, as closed as necessary’.